Improve generated Swagger spec compatibility with Endpoints Portal

[clementdenis]

• Support Endpoints Portal authorization flow

• Add authorizationUrl and useScopesInAuthFlow issuer config params
• Define default authorizationUrl for Google id token issuers
• Add scopes in operation's security (required for Try it! in Portal)
• Add authorizationUrl in OAuth2 flow (required for Try it! in Portal)
• Reorder Google id token issuers to have https:// one first

• New supported Swagger features

• Support deprecation on Swagger operations with @deprecated
• Add tags to Swagger operations to group like API Explorer in Portal
• Inline Map types (including JsonMap) to avoid useless definitions
• Set default values for parameters
• Add proper collection format (multi instead of csv)
• List unsupported features of the spec in UNSUPPORTED_FEATURES.md

• Order consistency

• Remove ordering attempt in reflection-based introspection
• Add ordering in Swagger generation (sort paths by string order)

• Testing

• Improve coverage of SwaggerGenerator (array tests)
• Extract Swagger assertion logic in a truth.dev subject
• Update truth.dev to 1.0

• Cleanup

• Remove writeInternal boolean in SwaggerGenerator (not used)

[codecov-io]

Codecov Report

Merging #34 into master will increase coverage by 0.46%.
The diff coverage is 89.44%.

@@             Coverage Diff             @@
##             master     #34      +/-   ##
===========================================
+ Coverage     81.14%   81.6%   +0.46%     
- Complexity     1738    1775      +37     
===========================================
  Files           159     159              
  Lines          6432    6495      +63     
  Branches        842     856      +14     
===========================================
+ Hits           5219    5300      +81     
+ Misses          900     875      -25     
- Partials        313     320       +7

Impacted Files	Coverage Δ	Complexity Δ
.../main/java/com/google/api/server/spi/Constant.java	0% <ø> (ø)	0 <0> (ø)	⬇️
...ogle/api/server/spi/tools/GetOpenApiDocAction.java	38.46% <0%> (ø)	3 <0> (ø)	⬇️
.../google/api/server/spi/config/model/ApiConfig.java	95.09% <0%> (ø)	69 <0> (ø)	⬇️
...le/api/server/spi/config/model/ApiClassConfig.java	64.81% <0%> (ø)	30 <0> (ø)	⬇️
...e/api/server/spi/config/model/ApiMethodConfig.java	83.75% <100%> (+0.33%)	72 <2> (+2)	⬆️
...server/spi/config/annotationreader/IssuerUtil.java	88.88% <100%> (+0.65%)	8 <0> (ø)	⬇️
.../api/server/spi/config/model/SchemaRepository.java	93.67% <100%> (+0.04%)	39 <2> (+2)	⬆️
...rver/spi/config/model/ApiIssuerAudienceConfig.java	91.66% <50%> (-3.99%)	14 <2> (+1)
.../api/server/spi/config/model/ApiIssuerConfigs.java	78% <60%> (+0.22%)	12 <1> (ø)	⬇️
...m/google/api/server/spi/MethodHierarchyReader.java	68.25% <75%> (-0.5%)	19 <1> (-1)
... and 6 more

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[alarribeau]

It looks ok but to be honest I can't assure it. Let's merge and see :)
(It could have been splited in various PRs and/or commits. For remaining swagger features, if we do support them, I suggest to create 1 PR by feature).

[RaHery]

+1

Reviewed 1 of 40 files at r1.
Reviewable status: 1 of 40 files reviewed, all discussions resolved (waiting on @llbrt and @RaHery)

[RaHery]

Reviewable status: 1 of 40 files reviewed, all discussions resolved (waiting on @llbrt and @RaHery)

[RaHery]

Reviewed 39 of 40 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @llbrt)

[llbrt]

idem,

Reviewed 40 of 40 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[llbrt]

Reviewable status: complete! all files reviewed, all discussions resolved

[RaHery]

Reviewable status: complete! all files reviewed, all discussions resolved