Support for `DateTime` custom scalar

[martinbonnin]

Use case

The DateTime scalar is specified at https://scalars.graphql.org/andimarek/date-time

If the codegen schema contains such a scalar:

scalar DateTime @specifiedBy(url: "https://scalars.graphql.org/andimarek/date-time")

We could detect it at build time automatically and map it to kotlinx.datetime.DateTime

Pros:

• kotlinx.datetime.DateTime is better to use compared to Any (current solution)
• no configuration to be made

Cons:

• could be surprising if the user doesn't want kotlinx.datetime.DateTime but maybe java.time.DateTime or some other custom class
• pulls kotlinx-datetime in the dependencies

Questions:

• should it be opt-in or opt-out?
• are the current adapters compatible?

[BoD]

pulls kotlinx-datetime in the dependencies

Because of this it would probably be preferable to keep it as an opt-in IMHO. So opt-in could be 2 steps: 1. set some flag to true 2. add the dependency(ies)

[martinbonnin]

Because of this it would probably be preferable to keep it as an opt-in IMHO

Just to be clear, the proposal is to pull kotlinx-datetime only if the schema contains DateTime scalars. All other users would be non-affected

[martinbonnin]

Just to be clear, the proposal is to pull kotlinx-datetime only if the schema contains DateTime scalars. All other users would be non-affected

Although that would require parsing the schema at Gradle configuration time which doesn't sound great. But maybe acceptable 🤷

[BoD]

To check: is one of the current adapters we have over here already compatible with https://scalars.graphql.org/andimarek/date-time?