feat: add listing endpoints, complete branches swagger-spec (4.0)

Description

• Add endpoints for listing snapshots, clones and branches
• Complete SwaggerUI Spec for branches

Related issue

Examples

GET /snapshots

[
    {
        "id": "oldest5@snapshot_20230515202911",
        "createdAt": "2023-05-15T20:30:35Z",
        "dataStateAt": "2023-05-15T20:29:11Z",
        "physicalSize": 0,
        "logicalSize": 74491392,
        "pool": "oldest5",
        "numClones": 1
    }
]

GET /clones

[
    {
        "id": "chh9ed61q2ss73cgvbkg",
        "snapshot": {
            "id": "oldest5@snapshot_20230515202911",
            "createdAt": "2023-05-15T20:30:35Z",
            "dataStateAt": "2023-05-15T20:29:11Z",
            "physicalSize": 0,
            "logicalSize": 74491392,
            "pool": "oldest5",
            "numClones": 1
        },
        "branch": "",
        "protected": false,
        "deleteAt": null,
        "createdAt": "2023-05-15T20:33:56Z",
        "status": {
            "code": "OK",
            "message": "Clone is ready to accept Postgres connections."
        },
        "db": {
            "connStr": "host=localhost port=6000 user=alice dbname=postgres",
            "host": "localhost",
            "port": "6000",
            "username": "alice",
            "password": "",
            "dbName": ""
        },
        "metadata": {
            "cloneDiffSize": 334336,
            "logicalSize": 74292224,
            "cloningTime": 0.449556853,
            "maxIdleMinutes": 2
        }
    }
]

GET /branches

[
    {
        "name": "main",
        "parent": "-",
        "dataStateAt": "20230515202911",
        "snapshotID": "oldest5@snapshot_20230515202911"
    },
    {
        "name": "001-branch",
        "parent": "main",
        "dataStateAt": "20230515202911",
        "snapshotID": "oldest5@snapshot_20230515202911"
    }
]

Checklist

• MR description has been reviewed
• MR changes are functionally tested
• MR does NOT have API/CLI changes OR there are API/CLI changes and they have been reviewed & DOCS ARE ADJUSTED (reference doc, etc)
• MR does NOT have UI changes OR there are UI changes and they have been reviewed & UX IS REVIEWED