feat(agents-api): Allow developers to optionally specify and set the UUID when creating (agent, session, user) objects through the REST API

[creatorrr]

trafficstars

Need to change the following code:

• openapi.yaml: allow id parameter as optional uuid string in POST /agents, /users, /sessions

And check if id parameter was passed in the POST handler, if not, then generate a new one:

• agents-api/agents_api/routers/agents/routers.py
• agents-api/agents_api/routers/users/routers.py
• agents-api/agents_api/routers/sessions/routers.py