Add GQL interface for project observability logs

What does this MR do and why?

• Adds a new observabilityLogsLinks GraphQL edge to ProjectType.
• Adds required types and resolver to implement it.
• Adds specs, including changes to other files as well as request specs for the new GraphQL interface.

Database queries

All records for a project

(These are from locally generated data since the table is brand new)

This query reads from an index condition as expected.

SELECT "observability_logs_issues_connections".* FROM "observability_logs_issues_connections" WHERE "observability_logs_issues_connections"."project_id" = 15;

                                                                       QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------
 Index Scan using index_observability_logs_issues_connections_on_project_id on observability_logs_issues_connections  (cost=0.15..7.43 rows=17 width=69)
   Index Cond: (project_id = 15)
(2 rows)

Selecting an individual record for a project

Query uses same index condition as above, and then filters on specific criteria. This will likely never return more than 1 or 2 records.

SELECT "observability_logs_issues_connections".* FROM "observability_logs_issues_connections" WHERE "observability_logs_issues_connections"."project_id" = 15 AND "observability_logs_issues_connections"."log_timestamp" = '2024-07-27 16:20:33.215711' AND "observability_logs_issues_connections"."service_name" = 'test' AND "observability_logs_issues_connections"."severity_number" = 4 AND "observability_logs_issues_connections"."trace_identifier" = 'aaaaa' AND "observability_logs_issues_connections"."log_fingerprint" = 'fsdfdsfs';

                                                                                                             QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Index Scan using index_observability_logs_issues_connections_on_project_id on observability_logs_issues_connections  (cost=0.15..7.64 rows=1 width=69)
   Index Cond: (project_id = 15)
   Filter: ((log_timestamp = '2024-07-27 16:20:33.215711+00'::timestamp with time zone) AND (service_name = 'test'::text) AND (severity_number = 4) AND (trace_identifier = 'aaaaa'::text) AND (log_fingerprint = 'fsdfdsfs'::text))
(3 rows)

MR acceptance checklist

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Before	After

How to set up and validate locally

1. Ensure you're using an Ultimate namespace.

2. Enable the :observability_features feature flag.

3. Create a new project, within an Ultimate group.

4. Create a new issue, and note its ID.

5. On a rails console, create a linked log for that project.

   issue_id = {{ID}}
   a = a = Observability::LogsIssuesConnection.create(issue: Project.find(issue_id).issues.last, severity_number: 12, service_name: 'gitlab-rails', trace_identifier: '23489affd', log_fingerprint: 'aaaaaa', log_timestamp: 2.days.ago)
   a.save! # Raise an exception if something went wrong.

6. For the created log, we can query a list of links - note the format of the timestamp should be iso8601.

   query {
     project(fullPath: "Flightjs/Flight") {
       id
       observabilityLogsLinks(timestamp: "2024-08-13T11:02:24.262999Z", severityNumber: 12, serviceName: "gitlab-rails", fingerprint: "abcdefghi", traceIdentifier: "23489affd") {
         nodes {
           timestamp
           severityNumber
           serviceName
           fingerprint
           traceIdentifier
           issue {
             title
             webUrl
           }
         }
       }
     }
   }

7. If successful, it should return a list of observabiltyLogsLinks, each representing the link between an observabililtyLog and its issue (if queried, as above)

   {
     "data": {
       "project": {
         "id": "gid://gitlab/Project/7",
         "observabilityLogsLinks": {
           "nodes": [
             {
               "timestamp": "2024-08-13T11:02:24Z",
               "severityNumber": 12,
               "serviceName": "gitlab-rails",
               "fingerprint": "abcdefghi",
               "traceIdentifier": "23489affd",
               "issue": {
                 "title": "fdfsdfsdfsdfsdfs",
                 "webUrl": "http://127.0.0.1:3000/flightjs/Flight/-/issues/40"
               }
             }
           ]
         } 
       }
     }
   }

Related to gitlab-org/opstrace/opstrace#2907 (closed)