Avoid using existing branches

[Nishnha]

What are you trying to accomplish?

Avoid using existing branch names.

Anything you want to highlight for special attention from reviewers?

Receives a list of existing dependabot/ branches from API, and uses that to determine if the branch name requires a suffix.

How will you know you've accomplished your goal?

Dependabot will avoid opening a PR with an existing branch name and will instead append a suffix to the branch name.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.

[kbukum1]

LGTM