Add Ormin ORM support for BaraDB (Nim client)

clients/nim/ormin/examples/chat/server.nim

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+import ../../ormin / [serverws]
+import ../../ormin
+
+import json
+
+# Ormin needs to know about our SQL model:
+importModel(DbBackend.sqlite, "chat_model")
+
+# Currently Ormin assumes a global database connection that needs to be
+# annotated as '.global' for technical reasons. Later versions will improve.
+var db {.global.} = open("chat.db", "", "", "")
+
+# Ormin produces the file "chatclient.nim" for our frontend:
+protocol "chatclient.nim":
+  # A 'common' code section is shared by both the client and the server:
+  common:
+    when not defined(js):
+      type kstring = string
+    type
+      inetType = kstring
+      varcharType = kstring
+      timestampType = kstring
+      intType = int
+
+
+  server "get recent messages":
+    let lastMessages = query:
+      select messages(content, creation, author)
+      join users(name)
+      orderby desc(creation)
+      limit 100
+    send(lastMessages)
+
+  client "get recent messages":
+    type TextMessage* = ref object
+    # Ormin fills in the fields of 'TextMessage' for us, based on the
+    # query in the 'server' part.
+    var allMessages*: seq[TextMessage] = @[]
+    proc getRecentMessages*()
+    allMessages = recv()
+
+
+  server "send chat message":
+    let userId = arg["author"].num
+    # unregistered users cannot send anything:
+    if userId == 0: return
+    query:
+      insert messages(content = %arg["content"], author = ?userId)
+    query:
+      update users(lastOnline = !!"DATETIME('now')")
+      where id == ?userId
+
+    let lastMessage = query:
+      select messages(content, creation, author)
+      join users(name)
+      orderby desc(creation)
+      limit 1
+
+    broadcast(lastMessage)
+
+  client "send chat message":
+    proc sendMessage*(m: TextMessage)
+    allMessages.add recv(TextMessage)
+
+
+  # This is the request to register/login a new user:
+  server "register/login a new user":
+    var candidates = query:
+      produce nim
+      select users(id, password)
+      where name == %arg["name"]
+    if candidates.len == 0:
+      let userId = query:
+        produce nim
+        insert users(name = %arg["name"], password = %arg["password"])
+        returning id
+      send(%userId)
+    else:
+      block search:
+        for c in candidates:
+          if c[1] == arg["password"].str:
+            send(%c[0])
+            echo "login found!"
+            break search
+        # invalid login:
+        send(%0)
+        echo "no such user!"
+
+  client "register/login a new user":
+    proc registerUser*(u: User)
+    var userId: int
+    userId = recv()
+    if userId == 0: setError(username, "invalid login!")
+
+
+serve "orminchat", dispatch