feat: Tesla.Middleware.JSON: Add support for Elixir 1.18's JSON module

[adamu]

This is a proposal for one way to add support to the built-in JSON module available in Elixir 1.18.

There were a few challenges with this, because Tesla makes assumptions about how an engine should behave that JSON doesn't conform to. To work around this I created a JSONAdapter module that conforms to Tesla's expectations, and allows users to simply specify

engine: JSON

for common cases, which will give people an easy path to migrate away from Jason, for example.

Elixir's built-in JSON module also supports custom encoders and decoders, which could theoretically be supplied via this middlewear's engine_opts param. But considering that would require additional wrapper/adapter logic, and the same thing can be achieved using the encoder: and decoder: options, I decided that might be overkill.

Long term, I don't think the :engine option makes much sense, because there are too many assumptions involved without defining a proper behaviour. Perhaps deprecating it and focussing on the :encoder and :decoder options might make sense?

Docs preview

Related issues

• Default Tesla.Middleware.JSON engine to JSON module for Elixir 1.18 #743

[yordis]

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