REST APIs for events.

[MUzairS15]

Notes for Reviewers

This PR fixes adds REST APIs for events.

1. /api/v2/events: Get all events belonging to the logged in user. (This particular API will be changed to /api/events once the UI is compeltely updated to use new events and SSE is tunred off, otherwise existing events will break.)
   Supported query params:
2. ?page : Defaults to page 1
3. ?pagesize: Defaults to 25, to get all events set ?pagesize=all
4. ?sort: Column to sort the results on, defaults to updated_at.
5. ?order: Sort order for the results, defaults to ascending.
6. ?category: Filter events based on event category, expects an array. eg: ?category=[connection, application,...]
7. ?severity: Filter events based on event severity, expects an array. eg: ?severity=[informational, error,...]
8. ?action: Filter events based on event action, expects an array. eg: ?action=[create, delete,...]
9. ?search: Search based one event description. (Not requried now, but have added incase)

API response:

{
  "events": [
    {
      "acted_upon": "1cfd0da5-3c6e-a2a5-eb1b-f6a7cd55f402",
      "action": "registering",
      "category": "connection",
      "created_at": "2023-09-01T16:43:33.548017+05:30",
      "description": "",
      "id": "12ere4-sew33-23asds-er45-49s56w2",
      "metadata": null,
      "operation_id": "25e5524f-3e08-42a5-a1f3-a12e73d54de4",
      "severity": "informational",
      "status": "",
      "system_id": "f7368f43-0d14-4e6a-918b-5dbef07aaafb",
      "updated_at": "2023-09-01T16:43:33.548168+05:30",
      "user_id": "b6467d0a-f11e-4614-9eb2-ab80c4f1c58d"
    }
  ],
  "page": 1,
  "page_size": 1,
  "count_by_severity_level": [
    {
      "severity": "error",
      "count": 23
    },
    {
      "severity": "informational",
      "count": 60
    },
    {
      "severity": "warning",
      "count": 93
    }
  ],
  "total_count": 65
}

page, pagesize, totalcount, count_by_severity_level are always returned`.

2. /api/events/status/{id}:

Update event's status associated with id.

Response: Updated event.

 {
      "acted_upon": "00000000-0000-0000-0000-000000000000",
      "action": "flush",
      "category": "meshsync",
      "created_at": "2023-09-02T18:52:59.092049+05:30",
      "description": "No Kubernetes context specified, please choose a context from context switcher",
      "id": "93f33cc1-f1e4-416d-9177-1c239bf3c0e0",
      "metadata": null,
      "operation_id": "d6019752-f7a1-4af3-a5f2-d30d2158e51d",
      "severity": "error",
      "status": "unread",
      "system_id": "d24217ff-a41f-4215-933c-a6ed2f599a50",
      "updated_at": "2023-09-05T22:09:29.247692+05:30",
      "user_id": "b6467d0a-f11e-4614-9eb2-ab80c4f1c58d"
    }

3. /api/events/{id}:
   Delete event associated with id.
   Signed commits

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