feat: add support for quotaProjectId header

[codyoss]

No description provided.

[codyoss]

After this change a release will need to be cut and core updated in order to make the proper changes there.

[codecov]

Codecov Report

Merging #826 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #826      +/-   ##
============================================
+ Coverage     78.69%   78.71%   +0.02%     
- Complexity     1145     1146       +1     
============================================
  Files           202      202              
  Lines          5092     5098       +6     
  Branches        404      405       +1     
============================================
+ Hits           4007     4013       +6     
  Misses          912      912              
  Partials        173      173

Impacted Files	Coverage Δ	Complexity Δ
...om/google/api/gax/rpc/ApiClientHeaderProvider.java	90% <100%> (+0.93%)	10 <0> (+1)	⬆️

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[codecov-io]

Codecov Report

Merging #826 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #826      +/-   ##
============================================
+ Coverage     78.69%   78.71%   +0.02%     
- Complexity     1145     1146       +1     
============================================
  Files           202      202              
  Lines          5092     5098       +6     
  Branches        404      405       +1     
============================================
+ Hits           4007     4013       +6     
  Misses          912      912              
  Partials        173      173

Impacted Files	Coverage Δ	Complexity Δ
...om/google/api/gax/rpc/ApiClientHeaderProvider.java	90% <100%> (+0.93%)	10 <0> (+1)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e0abb5c...110f6a0. Read the comment docs.

thanks for adding docs

[chingor13]

The gapic-only clients don't use google-cloud-core so there must be another place in the gax that would use this.

[codyoss]

I think you are right. Looks like there is one spot that it is possible it does not get set when making a JWT ServiceAccount in GoogleCredentialsProvider. I will add this in a followup PR once googleapis/google-auth-library-java#383 is merged and released.

[broady]

What's the meaning of the token suffix? A project ID doesn't match with the common understanding of "token"

[codyoss]

@broady nothing special. Looking at the others properties of the builder, it did not seem like Token applied to them either(at least not all). I could be wrong on this though as the class does not document what its properties are for. So I went with consistency of api related to other fields. If you think it is right though, we can drop the suffix. I will have to just deprecate the old one though for now as a release has already happened.

[broady]

@codyoss I looked more, it looks like "token" really only makes sense for constructing the client string.

I think "resource token" and "quota project id token" don't make sense.

Seems fine to leave as-is if users aren't typically interacting with this package.