Feature request: text pattern based code ownership.

[jaimevp54]

This feature would allow defining regex patterns to specify owners.
This could be useful when developers are interested in reviewing the usage of a particular variable, function or feature.

Examples:

Assuming the syntax: <file_path>:<regex>

# Match any file diff with the text `.select_related(` on it
**/*.py:\.select_related\( @user  

# Match any files in a `migrations` directory that include `DeleteModel` 
**/migrations/*.py:DeleteModel @user  

# Owner definitions without patterns should still be valid
# Match all files
*