Enable synchronization of feature flags to Jira

What does this MR do?

This MR enables the feature flag synchronization module in our JiraConnect app.

See this Atlassian documentation for a description of the protocol:

https://developer.atlassian.com/cloud/jira/software/rest/api-group-feature-flags/#api-featureflags-0-1-bulk-post

This feature has been tested (behind the feature flag) in staging and production.

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #296990 (closed)