Configurable commit author

**Currently**\
The current database user is used as a commit author (usually `root`).
Optionally, if Dolt-Workbench is running in a docker container, there seems to be an option to use Http-Proxy headers as an alternate commit author.

**Why this is not enough**\
One could add a new database user with the correct credentials, but from a quick look this does not include an authors e-mail. Plus, for dolt cli, we need to configure the commit author regardless.

The commit history then includes a bunch of "root"-authors which makes it impossible to distinguish commits by different authors. Bonus points if you try to use these commits on a collab-platform like DoltLab, where the link to the author is broken because it just links to the provided author name (instead of the account that pushed the commits).

**New Feature request**\
Ideally, Dolt Workbench can use the author configured in `dolt config`, so setting up new team members only requires adding their credentials there. Alternatively, Dolt Workbench uses its own configuration environment for a similar result.

During commit, the user can then select which credentials to use for the commit (maybe provide a way to choose a default)