Fix domain for video block LMS Root used for YT metadata

[bryanlandia]

Change description

In video_module, get customer domain (including custom domain override) for the LMS root URL used as the prefix for requests to the block handler that retrieves metadata from YouTube. It's been using tahoe.appsembler.com, which results in a 302 to login, then a CORS error from the handler.

Type of change

• Bug fix (fixes an issue)
• New feature (adds functionality)

Related issues

https://appsembler.atlassian.net/browse/ENG-97

Checklists

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• "Ready for review" label attached and reviewers assigned
• Changes have been reviewed by at least one other contributor
• Pull request linked to task tracker where applicable

[github-actions]

Checking git merge conflicts against https://github.com/edx/edx-platform.git

Comparing with	open-release/nutmeg.master
Benchmark conflicts with main	298
Current conflicts	299
Summary	Adds 1 new conflicts. How can we do better?

New conflicting files with 'open-release/nutmeg.master'

common/lib/xmodule/xmodule/video_module/video_module.py

Comparing with	master
Benchmark conflicts with main	313
Current conflicts	315
Summary	Adds 2 new conflicts. How can we do better?

New conflicting files with 'master'

xmodule/video_block/video_block.py