This commit adds validation for course advanced settings. Currently when course
administrators make invalid changes in the Settings/Advanced Settings tab,
they're not notified through a new modal window of the list of invalid settings
changes.
* Extending CourseMetadata
- Previously, we only had update_from_json method in CourseMetadata.py,
and it was only validating one field every POST request.
- Now we have validate_and_update_from_json method that encapsulates the
functionality of update_from_json into a validation call
- To avoid discrepancy of validation standards between modules, validation
uses the from_json method implemented to each field in xblock.
* Different Response in advanced settings ajax requests
- After receiving a POST ajax request, course.py calls
validate_and_update_from_json, and sends a json object of either:
1) valid course metadata model
2) error objects
* Error Messages shown in validation-error-modal
- error objects passed through ajax are shown in a separate modal.
This commit implements STUD-1490, allowing creation of components
on the container page. It also enables the delete and duplicate
buttons now that new content can be created that would benefit.
Note that it also creates shared functionality for adding components,
and refactors the unit page to use it too.
