Create sessions API

[dannykopping]

Depends on #1336

Sessions are sets of interceptions (or threads (#1338)).
If a session ID is not present for an interception, the individual interception should be treated as a session with a single interception and the session ID = interception ID.

Acceptance criteria:

• Added API endpoints with same filters as /api/v2/aibridge/interceptions (plus session ID), and pagination
  • GET /api/v2/aibridge/interceptions/by-session
  • GET /api/v2/aibridge/sessions/:id/interceptions (just an alias for GET /api/v2/aibridge/interceptions/by-session?session-id={id}, displaying only a single session - no list)
    • Database queries added to facilitate these
• Tests added

---

GET /api/v2/aibridge/interceptions/by-session

Just returns an aggregation of each interception.

Hit GET /api/v2/aibridge/sessions/:id/interceptions for the full output.

{
    "count": 99,
    "sessions": [
        {
            "session_id": "session_id|interception_id",
            "interceptions": [
                {
                    "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
                    "api_key_id": "string",
                    "started_at": "2019-08-24T14:15:22Z",
                    "ended_at": "2019-08-24T14:15:22Z",
                    "provider": "string",
                    "models": ["string", "string"],
                    "prompt": "string",
                    "initiator": {
                        "avatar_url": "http://example.com",
                        "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
                        "name": "string",
                        "username": "string"
                    },
                    "tokens_total": {
                        "input": 123, // input + cache reads
                        "output": 456
                    },
                    "tool_calls_total": 5
                }
            ]
        }
    ]
}

GET /api/v2/aibridge/sessions/:id/interceptions

{
    "count": 5,
    "session_id": "session_id|interception_id",
    "interception": {
        "api_key_id": "string",
        "ended_at": "2019-08-24T14:15:22Z",
        "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
        "initiator": {
            "avatar_url": "http://example.com",
            "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
            "name": "string",
            "username": "string"
        },
        "metadata": {
            "property1": null,
            "property2": null
        },
        "model": "string",
        "provider": "string",
        "started_at": "2019-08-24T14:15:22Z",
        "token_usages": [
            {
                "created_at": "2019-08-24T14:15:22Z",
                "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
                "input_tokens": 0,
                "interception_id": "34d9b688-63ad-46f4-88b5-665c1e7f7824",
                "metadata": {
                    "property1": null,
                    "property2": null
                },
                "output_tokens": 0,
                "provider_response_id": "string"
            }
        ],
        "tool_usages": [
            {
                "created_at": "2019-08-24T14:15:22Z",
                "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
                "injected": true,
                "input": "string",
                "interception_id": "34d9b688-63ad-46f4-88b5-665c1e7f7824",
                "invocation_error": "string",
                "metadata": {
                    "property1": null,
                    "property2": null
                },
                "provider_response_id": "string",
                "server_url": "string",
                "tool": "string"
            }
        ],
        "user_prompts": [
            {
                "created_at": "2019-08-24T14:15:22Z",
                "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",
                "interception_id": "34d9b688-63ad-46f4-88b5-665c1e7f7824",
                "metadata": {
                    "property1": null,
                    "property2": null
                },
                "prompt": "string",
                "provider_response_id": "string"
            }
        ]
    }
}