Add the connector catalog and read-only connections API

connector_sessions already holds one row per signed-in account or MCP
server. Migration 0038 names each row (connector_key, auth_kind,
display_name, account_label) and lets sources and tools point at the
row they use through connection_id, backfilling the links it can prove.

docsgpt/connectors/catalog.py declares every service DocsGPT connects
to, with the server settings it needs and what a connection provides.
New endpoints: GET /api/connectors/catalog, GET /api/connections,
GET /api/connections/<id> and POST /api/connections/<id>/disconnect.
/api/available_tools now groups tools into built_in, service and
custom, and source listings carry connectionId.

docsgpt/api/user/sources/routes.py

@@ -67,6 +67,12 @@ def _get_provider_from_remote_data(remote_data):
     return None
 
 
+def _connection_id(row: dict) -> str | None:
+    """The connection a source syncs from, as a string id, or None."""
+    value = row.get("connection_id")
+    return str(value) if value else None
+
+
 @sources_ns.route("/sources")
 class CombinedJson(Resource):
     @api.doc(description="Provide JSON file with combined available indexes")
@@ -117,6 +123,7 @@ class CombinedJson(Resource):
                     "config": SourceConfig.parse(index.get("config")).model_dump(),
                     "ownership": ownership,
                     "team_access": team_access,
+                    "connectionId": _connection_id(index),
                 }
 
             for index in indexes:
@@ -207,6 +214,7 @@ class PaginatedSources(Resource):
                         "team_access": (
                             None if owned else team_shared.get(str(doc["id"]))
                         ),
+                        "connectionId": _connection_id(doc),
                     }
                 )
             response = {

docsgpt/api/user/tools/routes.py

@@ -19,6 +19,7 @@ from docsgpt.api import api
 from docsgpt.api.pat.rules import filter_listing
 from docsgpt.api.user.artifacts.authz import Principal, authorize_artifact
 from docsgpt.api.user.team_sharing import effective_write_owner, visible_with_access
+from docsgpt.connectors.catalog import definition_for_tool
 from docsgpt.core.settings import settings
 from docsgpt.core.url_validation import SSRFError, validate_url
 from docsgpt.security.encryption import decrypt_credentials, encrypt_credentials
@@ -186,6 +187,10 @@ def transform_actions(actions_metadata):
 
 tools_ns = Namespace("tools", description="Tool management operations", path="/api")
 
+# Tools the Connectors page adds through "Add custom connector" rather than
+# the Add Tool modal.
+_CUSTOM_CONNECTOR_TOOLS = {"mcp_tool": "custom_mcp", "api_tool": "custom_openapi"}
+
 
 @tools_ns.route("/available_tools")
 class AvailableTools(Resource):
@@ -202,6 +207,13 @@ class AvailableTools(Resource):
                 description = lines[1].strip() if len(lines) > 1 else ""
                 config_req = tool_instance.get_config_requirements()
                 actions = tool_instance.get_actions_metadata()
+                definition = definition_for_tool(tool_name)
+                if definition is not None:
+                    group, connector_key = "service", definition.key
+                elif tool_name in _CUSTOM_CONNECTOR_TOOLS:
+                    group, connector_key = "custom", _CUSTOM_CONNECTOR_TOOLS[tool_name]
+                else:
+                    group, connector_key = "built_in", None
                 tools_metadata.append(
                     {
                         "name": tool_name,
@@ -209,6 +221,8 @@ class AvailableTools(Resource):
                         "description": description,
                         "configRequirements": config_req,
                         "actions": actions,
+                        "group": group,
+                        "connector_key": connector_key,
                     }
                 )
         except Exception as err: