[Internal] Added Service.NamedIdMap

[andrewnester]

Changes

This new function on the service allows to get access to NameIdMap from service instead of list method as it was done previously.

Previously in code generation relying on .List.NameIdMap could lead to undetermenistic behaviour if there were more than 1 List operation on service. Why this is allowed, service can have only 1 name to id method anyway.

Thus, new Service.NamedIdMap will find NamedIdMap from all methods it has and if there are more than 1 - will panic.

Tests

Used here:

• make test passing
• make fmt applied
• relevant integration tests applied

[renaudhartert-db]

LGTM. It's a shame that the code of the current library doesn't allow us to handle this properly with an error but that is out of the scope of this PR.

https://go.dev/wiki/CodeReviewComments#dont-panic

[renaudhartert-db]

[nit] The description wasn't super clear to me. Is this an accurate rewrite?

Suggested change

	// NamedIdMap allows to retrieve a special NamedIdMap object from all methods
	// in the service which returns name-to-id mapping retrieval definition for all
	// entities of a type
	// If there are multiple NamedIdMap for the service, it will panic, because this is not allowed.
	// NamedIdMap returns the NamedIdMap corresponding to the service's list method
	// or nil if the service doesn't have a list method. This function panics if the
	// service has more than one list method as this is currently not supported.

[renaudhartert-db]

[nit] this makes it clear that n is not meant to be used outside of this if.

Suggested change

	n := v.NamedIdMap()
	if n != nil {
	if n := v.NamedIdMap(); n != nil {