Draft: Add additional JWT audiences when validating the Jira JWT token

What does this MR do and why?

1. Adds a new JSONB column called jira_connect_settings to the application_settings table
2. Adds a new setting called jira_connect_additional_audience_url and exposes this in the Admin area > Settings > GitLab for Jira app > Jira Connect Additional Audience URL field
3. If the additional audience is set, append this to the aud array during validation

These changes are to address an error that can occur when the JWT audiences mismatch. See the issue description in #498587.

References

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• #498587

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