Fix: Serialize resource type for unpersisted records (blank id)

[bf4]

Current behavior when id is nil returns: {data: null}

Closes #2132
Closes #2180

Regression from v0.10.5 to v0.10.6

Incidental changes in the PR

• genereralized inflection test helper
• refactored resource identifier tests to use more explicit assertions
• rolled resource identifier type tests into jsonapi type tests
• Added regression spec for defined type not being inflected, as referenced in JSON:API relationship tests no longer show v0.10.5 regression #2211

[bf4]

cc interested parties @InteNs @morhekil @yoda @beet @xn @Genkilabs @gambala

[xn]

Thanks!

[InteNs]

looks good!

[bf4]

Anything else before I release a 0.10.7? I think the only other regression is #2178

[Genkilabs]

Terrific! Thank you for this, and for including the CC in the related PR.
^_^

[beet]

Awesome, thanks @bf4 !

[bf4]

arguably, if serializer.object is nil, the return value should be nil, not { type: type}, and consider it a 'nil' identifier