tests: Multiple available Digest Auth strategies + Opting-in to a strategy

[deve-sh]

Adds integration tests for #1524

[deve-sh]

Clarification: We're opting-in to the available strategies from the get-go

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.34%. Comparing base (45114b3) to head (374fe12).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1531      +/-   ##
===========================================
+ Coverage    75.29%   75.34%   +0.05%     
===========================================
  Files           49       49              
  Lines         3789     3789              
  Branches      1085     1085              
===========================================
+ Hits          2853     2855       +2     
+ Misses         712      711       -1     
+ Partials       224      223       -1     

Flag	Coverage Δ
integration	65.92% <ø> (+0.15%)	⬆️
legacy	36.71% <ø> (ø)
unit	41.88% <ø> (ø)

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