Add support for explicit java.security.Provider to ServiceAccountCred…

[stian-svedenborg-gul-katt]

…entials

This enables the storage of service account credentials in external key storage such as remote KeyVaults or HSMs.

Fixes #410

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[stian-svedenborg-gul-katt]

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[codecov[bot]]

Codecov Report

Merging #411 into master will increase coverage by 0.13%. The diff coverage is 85%.

@@             Coverage Diff              @@
##             master     #411      +/-   ##
============================================
+ Coverage     79.53%   79.66%   +0.13%     
- Complexity      397      399       +2     
============================================
  Files            27       27              
  Lines          1803     1810       +7     
  Branches        188      188              
============================================
+ Hits           1434     1442       +8     
+ Misses          269      268       -1     
  Partials        100      100

Impacted Files	Coverage Δ	Complexity Δ
.../google/auth/oauth2/ServiceAccountCredentials.java	83.53% <85%> (+0.88%)	50 <6> (+2)	:arrow_up:

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[stian-svedenborg-gul-katt]

@elharo Comments fixed or answered.

[stian-svedenborg-gul-katt]

@elharo Hi any chance of this one getting some love soon? :)