When creating a session, ask for the name of the branch that will be created

[paulomorgado]

Feature summary

GitHub Copilot App makes up branch names and always prefixes those with the session's user name. Allow the user to choose the branch name.

What problem are you trying to solve?

Prefixing the branch with the username might disclose non-intended information when pushing to public repos.

Proposed solution

Ask the user for the branch name.
And working directory, since we are at it.

Workflow impact

No response

Installation context

No response

Additional context

No response