Implement a way to control the join specification used in class Query

[RKrahl]

Add an argument join_specs to the constructor of class Query that allows to override the join specification to be used in the created query for selected related objects. Do not emit QueryNullableOrderWarning or QueryOneToManyOrderWarning if the concerned relation is in join_specs. This has been discussed in #84.

Draft, still missing:

• documentation
• tests

[MRichards99]

Apologies for the delay in responding, I've been on leave for the past few days. This looks like a good solution to give users the option to use different joins.

I can see how I can implement this into DataGateway API - I'd use the setJoinSpecs() function directly rather than passing an argument in the query's constructor, but it's good to have both options. I believe the join keywords you've listed are the only ones that work - I couldn't get any others to work when I was testing before.

Let me know once you've finished with the branch and I'll test/implement it onto DataGateway.

[MRichards99]

I had a chance to test this for DataGateway's use case (I implemented the join specification changes into DataGateway API and then tested on the frontend) and I'm happy this works well for us.