Support running database migrations

Summary

Run Rails database migrations that are required for running Puma and Sidekiq. Version v2alpha1 of GitLab custom resource must support the minimal specification for the configuration and description of migrations, for example initial password.

Success criteria

• Migrations can be configured with a GitLab custom resource (version v2alpha1).
• Migrations run from the specification without using GitLab Chart.
• GitLab instance is accessible and usable from the specified external URL.
• The status of GitLab custom resource shows the state of migrations.