Discovery document improvements

[urmuzov]

added documentationLink property
@description for enum constants and fields

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[codecov-io]

Codecov Report

Merging #93 into master will decrease coverage by 0.15%.
The diff coverage is 42.85%.

@@             Coverage Diff              @@
##             master      #93      +/-   ##
============================================
- Coverage     79.47%   79.31%   -0.16%     
  Complexity     1621     1621              
============================================
  Files           154      154              
  Lines          5461     5478      +17     
  Branches        703      708       +5     
============================================
+ Hits           4340     4345       +5     
- Misses          847      854       +7     
- Partials        274      279       +5

Impacted Files	Coverage Δ	Complexity Δ
...com/google/api/server/spi/config/model/Schema.java	100% <ø> (ø)	2 <0> (ø)	⬇️
...e/api/server/spi/discovery/DiscoveryGenerator.java	84.76% <30%> (-2.87%)	51 <0> (ø)
.../api/server/spi/config/model/SchemaRepository.java	87.85% <54.54%> (-3.99%)	26 <0> (ø)

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[urmuzov]

@tangiel @bradfriedman Guys, please have a look. Changes are pretty shallow.

Can you help me to figure out where to add tests to cover changes?

[googlebot]

CLAs look good, thanks!

[tangiel]

Sorry for the super slow replies; if you're still up for it, you want to follow the test pattern found in SwaggerGeneratorTest and DiscoveryGeneratorTest. Basically write a test endpoint using the new annotations and confirm its output.

[clementdenis]

We've split the improvements brought by this PR and added some tests:

• Add documentation link in discovery files #121 for documentation links
• Add description on resource fields #132 for description on resource fields
• Add description on enum constants #133 for description on enum values

Maybe this one should be closed.