Enable catalyst source copying

[mjh1]

• This enables source copying at catalyst for upload tasks (and not transcode-file) by setting the SourceMp4 flag on the catalyst request.
• Removed unused function removeCredentials

[codecov[bot]]

Codecov Report

Merging #204 (e461247) into main (84726bf) will increase coverage by 0.62334%. The diff coverage is 12.50000%.

@@                 Coverage Diff                 @@
##                main        #204         +/-   ##
===================================================
+ Coverage   14.77750%   15.40084%   +0.62334%     
===================================================
  Files             19          19                 
  Lines           2382        2370         -12     
===================================================
+ Hits             352         365         +13     
+ Misses          2005        1981         -24     
+ Partials          25          24          -1     

Impacted Files	Coverage Δ
task/import.go	0.00000% <0.00000%> (ø)
task/upload.go	22.03742% <13.33333%> (+2.76764%)	:arrow_up:

... and 1 file with indirect coverage changes

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Impacted Files	Coverage Δ
task/import.go	0.00000% <0.00000%> (ø)
task/upload.go	22.03742% <13.33333%> (+2.76764%)	:arrow_up:

... and 1 file with indirect coverage changes