Features
- Add and implement `GitProject.default_branch` property, by [jpopelka](https://github.com/jpopelka), [#515](https://github.com/packit-service/ogr/pull/515)
- All git forges support changing of a default branch of a repo/project. All newly created Github projects have had 'main' as a default branch instead of 'master' [since October 2020](https://docs.github.com/en/free-pro-teamlatest/github/administering-a-repository/changing-the-default-branch).
- PagureService: Make retries parametrizable via `max_retries` argument, by [csomh](https://github.com/csomh), [#514](https://github.com/packit-service/ogr/pull/514)
- This way users of a PagureService object can control how failures of API calls are retried.