GH #2580: Remove use of Auth0 for NDLA audio and image API

[chrieinv]

Changes to the use of NDLA audio and image APIs to fix issues with H5P export sometimes failing if content from the API is used

• Use the API without Auth0
• Client side now access more of the API directly instead of through CA

[codecov[bot]]

Codecov Report

Merging #2582 (20a2a27) into master (ad4c05e) will increase coverage by 0.23%. The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #2582      +/-   ##
============================================
+ Coverage     62.55%   62.78%   +0.23%     
- Complexity     2728     2737       +9     
============================================
  Files           279      279              
  Lines         12145    12146       +1     
============================================
+ Hits           7597     7626      +29     
+ Misses         4548     4520      -28     

Components	Coverage Δ
contentauthor	62.78% <100.00%> (+0.23%)	:arrow_up: