[spaceship] Add to_json for ConnectAPI models

[tbodt]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

I wanted to write a script that dumps out the list of beta testers as JSON, but the ConnectAPI models didn't have to_json implemented, so I implemented it.

Description

Added a to_json method to ConnectAPI models that returns its attributes in JSON.

Testing Steps

bundle exec rspec spaceship/spec/connect_api/model_spec.rb

[max-ott]

Hi @tbodt thanks for the PR! More than happy to test it, do you have some easy testing steps so I can review it and move things forward?

[janpio]

The test you added @tbodt (Thanks for that!) doesn't seem to be to happy:

`Failures:

  1) Spaceship::ConnectAPI::Model #to_json
     Failure/Error:
       expect(JSON.parse(test.to_json)).to eq({
         "id" => "id",
         "foo" => "foo",
         "foo_bar" => "foo_bar"
       })

     TypeError:
       wrong element type Symbol at 0 (expected array)
     # ./spaceship/lib/spaceship/connect_api/model.rb:54:in `to_h'
     # ./spaceship/lib/spaceship/connect_api/model.rb:54:in `to_json'
     # ./spaceship/spec/connect_api/model_spec.rb:17:in `block (2 levels) in <top (required)>'

[tbodt]

It passed on my machine. Looks like it only works on ruby 2.6.

[tbodt]

Tests pass now :)

[joshdholtz]

Seems good to me! Thanks for the contribution 😊

[fastlane-bot]

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