feat(clients): add nim-allographer client with BaraDB driver support

- Pure Nim wire protocol client (async + sync, no C FFI)
- Query Builder: fluent API, SQL generator, execution, transactions
- Schema Builder: create/alter/drop tables, column operations
- Connection pool with aging and timeout handling
- ORM integration via compile-time DB_BARADB switch
- Tests: test_open, test_query
- Documentation: README.md, PLAN_BARADB.md

clients/nim-allographer/README.md

@@ -0,0 +1,204 @@
+allographer
+===
+
+[![nimble](https://raw.githubusercontent.com/yglukhov/nimble-tag/master/nimble.png)](https://github.com/yglukhov/nimble-tag)  
+![Build Status](https://github.com/itsumura-h/nim-allographer/workflows/Build%20and%20test%20Nim/badge.svg)
+
+
+An asynchronous query builder library inspired by [Laravel/PHP](https://readouble.com/laravel/6.0/en/queries.html) and [Orator/Python](https://orator-orm.com) for Nim.  
+Supported Databases are [Sqlite3](https://www.sqlite.org/index.html), [PostgreSQL](https://www.postgresql.org/), [MySQL](https://www.mysql.com/), [MariaDB](https://mariadb.org/) and **BaraDB**. (SurrealDB is planned to be supported in v3)  
+Supported Nim v2
+
+## Easy to access Rdb
+### Query Builder
+```nim
+import asyncdispatch, json
+import allographer/connection
+import allographer/query_builder
+
+let maxConnections = 95
+let timeout = 30
+let rdb = dbOpen(PostgreSQL, "database", "user", "password", "localhost", 5432, maxConnections, timeout)
+# also available
+# let rdb = dbOpen(SQLite3, "/path/to/db/sqlite3.db", maxConnections=maxConnections, timeout=timeout)
+# let rdb = dbOpen(MySQL, "database", "user", "password", "localhost", 3306, maxConnections, timeout)
+# let rdb = dbOpen(MariaDB, "database", "user", "password", "localhost", 3306, maxConnections, timeout)
+# let rdb = dbOpen(PostgreSQL, databaseUrl = asDatabaseUrl("postgresql://user:password@localhost:5432/database"), maxConnections=maxConnections, timeout=timeout)
+# let rdb = dbOpen(Baradb, "database", "user", "password", "localhost", 9472, maxConnections, timeout)
+# let surreal = dbOpen(SurrealDB, "test_ns" "test_db", "user", "password" "http://localhost", 8000, maxConnections, timeout)
+
+proc main(){.async.} =
+  let result = await rdb
+                    .table("users")
+                    .select("id", "email", "name")
+                    .limit(5)
+                    .offset(10)
+                    .get()
+  echo result
+
+waitFor main()
+
+>> SELECT id, email, name FROM users LIMIT 5 OFFSET 10
+>> @[
+  {"id":11,"email":"user11@gmail.com","name":"user11"},
+  {"id":12,"email":"user12@gmail.com","name":"user12"},
+  {"id":13,"email":"user13@gmail.com","name":"user13"},
+  {"id":14,"email":"user14@gmail.com","name":"user14"},
+  {"id":15,"email":"user15@gmail.com","name":"user15"}
+]
+```
+
+### Schema Builder
+```nim
+import allographer/schema_builder
+
+
+rdb.create([
+  table("auth", [
+    Column.increments("id"),
+    Column.string("name").nullable(),
+    Column.timestamp("created_at").default()
+  ]),
+  table("users", [
+    Column.increments("id"),
+    Column.string("name"),
+    Column.foreign("auth_id").reference("id").on("auth").onDelete(SET_NULL)
+  ])
+])
+
+>> CREATE TABLE auth (
+    id INT NOT NULL PRIMARY KEY,
+    name VARCHAR,
+    created_at DATETIME DEFAULT (NOW())
+)
+>> CREATE TABLE users (
+    id INT NOT NULL PRIMARY KEY,
+    name VARCHAR NOT NULL,
+    auth_id INT,
+    FOREIGN KEY(auth_id) REFERENCES auth(id) ON DELETE SET NULL
+)
+
+rdb.alter(
+  table("users", [
+    Column.string("email").unique().default("").add(),
+    Column.deleteColumn("name")
+  ])
+)
+
+>> ALTER TABLE "users" ADD COLUMN 'email' VARCHAR UNIQUE DEFAULT '' CHECK (length("email") <= 255)
+>> ALTER TABLE "users" DROP `name`
+```
+
+## Index
+<!--ts-->
+- [allographer](#allographer)
+  - [Easy to access Rdb](#easy-to-access-rdb)
+    - [Query Builder](#query-builder)
+    - [Schema Builder](#schema-builder)
+  - [Index](#index)
+  - [Install](#install)
+  - [Configuation](#configuation)
+  - [Createing connection](#createing-connection)
+  - [Logging](#logging)
+  - [Documents](#documents)
+  - [Nim API Documents](#nim-api-documents)
+    - [v2](#v2)
+  - [Development](#development)
+    - [Branch naming rule](#branch-naming-rule)
+
+<!-- Created by https://github.com/ekalinin/github-markdown-toc -->
+<!-- Added by: root, at: Mon Jul 17 07:46:10 UTC 2023 -->
+
+<!--te-->
+---
+
+## Install
+```sh
+nimble install allographer
+```
+
+If you get `SIGSEGV: Illegal storage access. (Attempt to read from nil?)` when trying to use the database you likely have a problem with the library path. On OS X the default is to check for the `brew --prefix` of the chosen driver, if that doesn't work it will look in `/usr/lib` or an environment variable `DYLD_xxx_PATH` where `xxx` if your driver: `SQLITE`, `MARIADB`, `MYSQL` or `POSTGRES`.
+
+## Configuation
+Allographer loads emvironment variables of `DB_SQLITE`, `DB_POSTGRES`, `DB_MYSQL`, `DB_MARIADB` and `DB_BARADB` to define which process should be **compiled**.<br>
+(`DB_SURREAL` is planned to be supported in v3)<br>
+These environment variables have to be set at compile time, so they have to be written in `config.nims` not in `.env`.
+
+config.nims
+```nim
+import os
+
+putEnv("DB_SQLITE", $true)
+putEnv("DB_POSTGRES", $true)
+```
+In this example, even if your runtime environment lacks `mysqlclient-dev`, execution will success. However if your runtime environment lacks `sqlite3`, execution will fail.
+
+## Createing connection
+Database connection should be definded as singleton variable.
+
+database.nim
+```nim
+import allographer/connection
+
+let rdb* = dbOpen(PostgreSQL, "database", "user", "password", "localhost", 5432, maxConnections, timeout)
+
+# you can create connection for multiple database at same time.
+let sqliteRdb* = dbOpen(Sqlite3, "/path/to/db/sqlite3.db", maxConnections=maxConnections, timeout=timeout)
+let mysqlRdb* = dbOpen(MySQL, "database", "user", "password", "localhost", 3306, maxConnections, timeout)
+let mariaRdb* = dbOpen(MariaDB, "database", "user", "password", "localhost", 3306, maxConnections, timeout)
+let pgUrlRdb* = dbOpen(PostgreSQL, databaseUrl = asDatabaseUrl("postgresql://user:password@localhost:5432/database"), maxConnections=maxConnections, timeout=timeout)
+let baradbRdb* = dbOpen(Baradb, "database", "user", "password", "localhost", 9472, maxConnections, timeout)
+# let surrealDb* = dbOpen(SurrealDb, "test_ns" "test_db", "user", "password" "http://localhost", 8000, maxConnections, timeout) # planned for v3
+```
+
+Then, call connection when you run query.
+
+run_sql.nim
+```nim
+import asyncdispatch
+import allographer/query_builder
+from database import rdb
+
+proc main(){.async.}=
+  echo await rdb.table("users").get()
+
+waitFor main()
+```
+
+## Logging
+Please set args in `dbOpen()`
+```nim
+proc dbOpen*(driver:Driver, database:string="", user:string="", password:string="",
+            host: string="", port=0, maxConnections=1, timeout=30,
+            shouldDisplayLog=false, shouldOutputLogFile=false, logDir=""):Rdb
+```
+- shouldDisplayLog: Whether display logging in terminal console or not.
+- shouldOutputLogFile: Whether output logging in log file or not.
+- logDir: Define logging dir path.
+
+
+## Documents
+[Schema Builder for RDB](./documents/rdb/schema_builder.md)  
+[Query Builder for RDB](./documents/rdb/query_builder.md)  
+[Schema Builder for SurrealDB](./documents/surrealdb/schema_builder.md) (planned for v3)  
+[Query Builder for SurrealDB](./documents/surrealdb/query_builder.md) (planned for v3)
+
+
+## Nim API Documents
+### v2
+[connection](https://itsumura-h.github.io/nim-allographer/v2/connection.html)  
+[Schema Builder](https://itsumura-h.github.io/nim-allographer/v2/schema_builder.html)  
+[Query Builder](https://itsumura-h.github.io/nim-allographer/v2/query_builder.html)
+
+
+## Development
+### Branch naming rule
+Please create this branch name when you will create a new pull request.
+
+| Branch | Description |
+| ------ | ----------- |
+| feature-*** | New feature branch |
+| hotfix-*** | Bug fix branch |
+| chore-*** | Chore work or maintenance |
+
+This naming rule automatically labels the pull request.