Adds additional query syntax for the CDA

[floriank]

After having no time for a while these days and thinking a bit about #38, I decided to put in some work about it.

This will add support for more complex queries as noted by @ryansch, in the form of:

Entries 
|> content_type("my_content_type") 
|> by(id: "my_id", number_of_warthogs: [lt: 42]) # or similar, no clue what offers the most benefits
|> fetch_all

and provide some safeguards around it, e.g. using by without a content_type call is not permitted, etc.

Feedback, as always, is very welcome.

TODO

• Entries by content_type
• Entries and Assets via by
• Array support in by, via [nin] and [in]
• Range support in by via [lte], [gte], [lt] and [gt]
• Existence support
• Full text support via query and [match]

Out of scope

• Full text per field
• Geolocation shenanigans
• filtering by mime types

Somebody create some issues for the ones above please 😉 (will probably do tomorrow)

Fixes #38.

[coveralls]

Pull Request Test Coverage Report for Build 8903f5c601181890f9d8e199d75cc7b270af06b7-PR-49

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 10 of 17 (58.82%) changed or added relevant lines in 2 files are covered.
• 23 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+6.4%) to 74.219%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/contentful/query.ex	9	16	56.25%

Files with Coverage Reduction	New Missed Lines	%
lib/contentful_delivery/delivery.ex	11	72.5%
lib/contentful/query.ex	12	57.45%

Totals
Change from base Build dd71b8856a05a54a02d2c8f2072b560d468f6a4d:	6.4%
Covered Lines:	95
Relevant Lines:	128

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💛 - Coveralls

[asaaki]

Looks quite good. I'm not a query expert though. 😅
Just tiny nits.

[asaaki]

I love it! 😍