protoc-gen-swagger, Fix for infinite loop on circular references in query parameters

[Romeren]

Added function nestedQueryParams in proto-gen-swagger/genswagger/template.go with map[string]bool parameter for keeping track of and detecting circular references.
Added test TestMessageToQueryParametersRecursive in proto-gen-swagger/genswagger/template_test.go for testing gracefully handling of circular references between messages.
See issue #1167

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[codecov-io]

Codecov Report

Merging #1266 into master will increase coverage by 0.15%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1266      +/-   ##
==========================================
+ Coverage   53.99%   54.14%   +0.15%     
==========================================
  Files          42       42              
  Lines        4369     4375       +6     
==========================================
+ Hits         2359     2369      +10     
+ Misses       1752     1750       -2     
+ Partials      258      256       -2     

Impacted Files	Coverage Δ
protoc-gen-swagger/genswagger/template.go	57.62% <100.00%> (+0.54%)	⬆️

---

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 01598a7...ea71c3c. Read the comment docs.

[Romeren]

@googlebot I signed it!

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

ℹ️ Googlers: Go here for more info.

[Romeren]

@googlebot I fixed it.

[Romeren]

@googlebot I fixed it

[johanbrandhorst]

This is fantastic! Thanks so much for putting this together, and I love your comments. A+, I've only got some grammatical comments, I think the more commonly used phrase for this sort of thing is cycle, so I've made some suggestions. Thanks for your contribution!

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

ℹ️ Googlers: Go here for more info.

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[Romeren]

Hmm... I seem to continuously run into issues with cla/google. It does not like my setup with multiple email accounts... but i think i have managed to get it working.

I have accepted all your requested changed

[johanbrandhorst]

Looks like a missed a few circle references, sorry!

[johanbrandhorst]

Thanks for your contribution! Could you please cherry pick this commit to v2?