feat: add list-my-workspaces operation and document IAM in API specs

Add a new `list-my-workspaces` operation so non-admin users can
discover which workspaces they have access to.  For OSS IAM, regular
users see their home workspace; admins see all workspaces.

Also add the full IAM service to both OpenAPI and AsyncAPI specs —
it was previously undocumented despite being a first-class service
on both HTTP and WebSocket interfaces.

trustgraph-base/trustgraph/base/iam_client.py

@@ -300,6 +300,14 @@ class IamClient(RequestResponse):
         )
         return resp.workspace
 
+    async def list_my_workspaces(self, actor="", timeout=IAM_TIMEOUT):
+        resp = await self._request(
+            operation="list-my-workspaces",
+            actor=actor,
+            timeout=timeout,
+        )
+        return list(resp.workspaces)
+
     async def list_workspaces(self, actor="", timeout=IAM_TIMEOUT):
         resp = await self._request(
             operation="list-workspaces",