Add method to GitRequirer to surface relations with errorneous data

### Problem statement

The airflow-coordinator charm surfaces an error (along with going into `BlockedStatus`) if the related git-integrator has data and the data does not include required fields

This seems a great candidate method/property to add to the `GitRequirer` class

### Enhancement Proposal

Add a method/property to the `GitRequirer` class that returns all relations/relation ids that are not well formatted. Exclude relations with no relation data (to disqualify relations waiting for the git-integrator to populate relation data as erroneous). This method/property can implement relation data validations to be executed on the requirer charm, and can also be used to improve `GitRequirer.is_ready()` implementation

### What needs to get done?

_No response_