Support RFC9457 by default

[miqui]

Echo should support RFC 9457 because it gives Go APIs a standard, machine-readable error format that clients can reliably parse, instead of every team inventing its own JSON error shape. RFC 9457 also keeps HTTP concerns out of business logic by cleanly mapping application errors to application/problem+json, which should fit Echo’s role as a lean framework for building APIs.

[aldas]

well the default error handler could be changed to know RFC 9457 type ala

type ProblemError struct {
	Type     string `json:"type"`
	Title    string `json:"title"`
	Status   int    `json:"status"`
	Detail   string `json:"detail,omitempty"`
	Instance string `json:"instance,omitempty"`
}

also maybe additional interface with mehtod that can return RFC 9457 type so your own error types can be converted to it

and write it as application/problem+json content type.

[aldas]

probably different error handler function is needed - one which only outputs these RFC 9457 by turning all other errors to it

[miqui]

Yeah, that makes sense. I can do a PR following your suggestions. Let me know.

[aldas]

PR for separate error handler function to output RFC 9457 structure is ok by me. maybe something can be combined with default or generalized, but this is not a must if it gets too complex solution - as they say sometimes little coping is better.

[miqui]

ok, @aldas fair enough. I should have a PR soon constrained with your thoughts. Which btw, I do agree.