Allow to resolve automatically Parse Type fields from Custom Schema

[Moumouls]

An error occur when you write a custom Mutation/Query that return an auto generated type like User, SomeClass...

For example, currently it fails

extend type Mutation {
   createASpecialUser(): User
}

So we need to inject Auto GraphQL Type fields into the custom one to return a valid User.
Also we need to avoid doing this for roots types to prevent wrong routing during schema execution.

[codecov]

Codecov Report

Merging #6562 into master will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6562      +/-   ##
==========================================
- Coverage   93.91%   93.88%   -0.04%     
==========================================
  Files         169      169              
  Lines       11967    11965       -2     
==========================================
- Hits        11239    11233       -6     
- Misses        728      732       +4     

Impacted Files	Coverage Δ
src/GraphQL/ParseGraphQLSchema.js	97.38% <100.00%> (-0.03%)	⬇️
src/Adapters/Storage/Mongo/MongoStorageAdapter.js	92.85% <0.00%> (-0.67%)	⬇️
src/RestWrite.js	93.81% <0.00%> (-0.17%)	⬇️

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[davimacedo]

@Moumouls can you please add a test case?

[Moumouls]

I will add test case soon, finally after many tests on my teams graphql parse server (with advanced GraphQL use), i figured out that a simple merge (transfer custom type to auto) combine to replace last types seems to solve all issues and all types/mutation/queries are correctly overloaded.

[Moumouls]

Postgres fail again

[Moumouls]

@davimacedo test case added !

[davimacedo]

LGTM