Don't initialize youtube resolver if youtube-api-key is empty

[M4tthewDE]

Pull request checklist:

• CHANGELOG.md was updated, if applicable

Description

Don't initialize youtube resolver if api key is empty. As far as I can tell from reading the source, the package we are using does not care about the api key being empty and does not return an error.

The test in intialize_test.go fails for me locally, but it passes in CI.
That might be worth an investigation?
Turns out google.golang.org/api/youtube/v3 automatically pulls in creentials from GOOGLE_APPLICATION_CREDENTIALS

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (a7a27dd) 47.22% compared to head (ccec2bd) 47.13%.

Files	Patch %	Lines
internal/resolvers/youtube/initialize.go	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #556      +/-   ##
==========================================
- Coverage   47.22%   47.13%   -0.09%     
==========================================
  Files          99       99              
  Lines        3733     3738       +5     
==========================================
- Hits         1763     1762       -1     
- Misses       1918     1923       +5     
- Partials       52       53       +1     

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