[19.0][ADD] endpoint_json2

[AungKoKoLin1997]

This module adds exec_mode="json2 to the endpoint framework, enabling declarative JSON-2 API endpoint configuration. Select a model, method, and parameters — the module handles dispatch, parameter validation, access control, and result filtering. A code snippet can be used as an alternative to a model method for quick, ad-hoc logic.

@qrtl QT6769

[simahawk]

@AungKoKoLin1997 interesting approach. Early feedback: I don't think the mixin is the right place as it can be inherited by all extending models (eg: edi_endpoint). I tend to say endpoint.endpoint is better.

[AungKoKoLin1997]

@simahawk Thanks for your feedback. I updated to use endpoint.endpoint instead of the mixin model.

[smorita7749]

Functional review: LGTM
The flow creating endpoint and getting response is properly working.

[simahawk]

@ivantodorovich can you have a look at this?

[yostashiro]

Code review and functional test.

[AungKoKoLin1997]

I added a few changes.

• Response Language (json2_lang_id): optionally forces the execution context language, so translated values (including dotted relational fields like uom_id.name) no longer depend on the API user's language setting.
• Response Timezone (json2_tz): optionally converts datetimes in the response to the given timezone, rendered as local wall time without an offset (incoming datetime parameters are left as-is).
• Align access / exec-target rules with the documentation: an empty Allowed Groups list rejects every caller, and Method / Code Snippet are truly mutually exclusive — both now backed by constraints so a data file or an import cannot create an endpoint that nobody can call, or one with both exec targets set.
• Response fields for non-read methods: plain field names are validated only for read / search_read, whose rows are made of model fields. Other methods can now declare their own keys instead of leaving json2_response_fields empty (which disables filtering and aliasing entirely). Dotted specs stay validated for every method.
• Tests: moved the test endpoints to their own route group so they no longer collide with the demo data route.