feat: Add OpenAI Conversations API (#3429)

# What does this PR do?

Initial implementation for `Conversations` and `ConversationItems` using
`AuthorizedSqlStore` with endpoints to:
- CREATE
- UPDATE
- GET/RETRIEVE/LIST
- DELETE

Set `level=LLAMA_STACK_API_V1`.

NOTE: This does not currently incorporate changes for Responses, that'll
be done in a subsequent PR.

Closes https://github.com/llamastack/llama-stack/issues/3235

## Test Plan
- Unit tests
- Integration tests

Also comparison of [OpenAPI spec for OpenAI
API](https://github.com/openai/openai-openapi/tree/manual_spec)
```bash
oasdiff breaking --fail-on ERR docs/static/llama-stack-spec.yaml https://raw.githubusercontent.com/openai/openai-openapi/refs/heads/manual_spec/openapi.yaml --strip-prefix-base "/v1/openai/v1" \
--match-path '(^/v1/openai/v1/conversations.*|^/conversations.*)'
```

Note I still have some uncertainty about this, I borrowed this info from
@cdoern on https://github.com/llamastack/llama-stack/pull/3514 but need
to spend more time to confirm it's working, at the moment it suggests it
does.

UPDATE on `oasdiff`, I investigated the OpenAI spec further and it looks
like currently the spec does not list Conversations, so that analysis is
useless. Noting for future reference.

---------

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

pyproject.toml

@@ -32,7 +32,7 @@ dependencies = [
     "jinja2>=3.1.6",
     "jsonschema",
     "llama-stack-client>=0.2.23",
-    "openai>=1.100.0",                                # for expires_after support
+    "openai>=1.107",                                # for expires_after support
     "prompt-toolkit",
     "python-dotenv",
     "python-jose[cryptography]",
@@ -49,6 +49,7 @@ dependencies = [
     "opentelemetry-exporter-otlp-proto-http>=1.30.0", # server
     "aiosqlite>=0.21.0",                      # server - for metadata store
     "asyncpg",                                # for metadata store
+    "sqlalchemy[asyncio]>=2.0.41",           # server - for conversations
 ]
 
 [project.optional-dependencies]