feat: Add TF versions updater

[bharathkkb]

Fixes #628

/cc @morgante

[codecov]

Codecov Report

Merging #629 (814d312) into master (cc7f39a) will increase coverage by 1.26%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #629      +/-   ##
==========================================
+ Coverage   80.73%   81.99%   +1.26%     
==========================================
  Files          45       46       +1     
  Lines        5418     5477      +59     
  Branches      410      441      +31     
==========================================
+ Hits         4374     4491     +117     
+ Misses       1043      985      -58     
  Partials        1        1              

Impacted Files	Coverage Δ
src/releasers/terraform-module.ts	91.30% <100.00%> (+58.63%)	⬆️
src/updaters/terraform/module-version.ts	100.00% <100.00%> (ø)

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[morgante]

@bharathkkb Can we add a test fixture for a submodule?

[bharathkkb]

@morgante sg, currently logic for submodule is in the releaser so we may need to add a test there.

release-please/src/releasers/terraform-module.ts

Line 90 in 25a9b52

// A module may have submodules, so find all versions.tf to update.

[bcoe]

@bharathkkb when adding tests for releasers, take a look at these tests:

https://github.com/googleapis/release-please/blob/master/test/releasers/simple.ts#L43

I've been switching to using sinon and mocking for tests, rather than nock (_which requires you enumerate every HTTP endpoint you hit with the GitHub API). I think you'll find sinon easier.

[bharathkkb]

@morgante @bcoe added some tests primarily testing the behavior for modules, modules+sub modules and backward compatibility if no versions.tf or module versions defined.