feat(GraphQL): add filterQueryOverride to GraphQL Service

[ghiscoding]

• similar approach to PR feat(OData): add filterQueryOverride to OData Service #1536 but for GraphQL Service
• adds a custom filterQueryOverride which provides a way for the user to override default filter operator and GraphQL query

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.8%. Comparing base (3882ce1) to head (6092bdd).

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #1549     +/-   ##
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+ Coverage    99.8%   99.8%   +0.1%     
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  Files         198     198             
  Lines       21685   21691      +6     
  Branches     7112    7253    +141     
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+ Hits        21624   21630      +6     
  Misses         55      55             
  Partials        6       6             

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[ghiscoding]

@zewa666 so I think I got a similar approach to your OData PR #1536, however 1 major thing that makes it apart is that instead of returning a string, I'm actually asking the user to return an object of the shape { field: string; operator: string; value: any; } which is what we end up with in the GraphQL query.

However, while doing this PR, I noticed that my GraphqlFilterQueryOverrideArgs is an exact copy of your OdataFilterQueryOverrideArgs, so I think it would be best if we merge them both into 1 interface which could maybe be named as BackendServiceFilterQueryOverrideArgs and because it's generic then I think you should also move it to a backend service interface (or a new file) like backendServiceOption.interface.ts. So would you mind doing that change in your PR? I can update my PR afterward by simply using that new interface.

I know you're using OData and not GraphQL, but it would still be nice if you could take a look at my PR and tell me if it makes any sense (I don't even have a GraphQL server to test with) but I followed this SO answer that inspired my approach which I think is correct: https://stackoverflow.com/a/37981802/1212166

[zewa666]

sure I'll take a look tonight. btw can you target my branch as destination for the merge? I'm genuinly interested if thats possible, but no probs I can move the files around as you mentioned anyways.

with regards to testing perhaps a quick way to ramp up a server with auto graphql features would be to look into Hasura. or if you just want to spin up a demo on top of json files perhaps https://github.com/marmelab/json-graphql-server

[zewa666]

aside from the small comment above LGTM