fix(#1975): Allow to use before/after/rescue_from methods in any order when using mount

[jcagarcia]

This PR tries to "fix" the issue described in #1975 .

Right now, as we can read in our README, declarations as before/after/rescue_from must be placed before mount in a case where they should be inherited.

However, I think this behavior arises from the existing implementation rather than being an intentional design. This occurs because when the mount method is invoked, a new Endpoint instance is generated, inheriting the previously registered before/after/rescue_from methods. However, if additional before/after/rescue_from methods are executed after the mount operation, the mounted endpoints remain unrefreshed.

Considering that:

1. Whenever a method is run within a Grape::API class, it is stored in the @setup variable in the sequence in which it was executed.
2. Upon completion of the execution, we will have an array containing the methods that were executed in the precise order they were called.

My proposal to address this issue is:

1. When executing any method, such as before/after/rescue_from (in fact, any method, not limited to these), verify whether there have been preceding mount method calls for this particular Grape::API class stored within the @setup variable.
2. If affirmative, re-apply the mounting of the same endpoint to update and refresh the inherited configurations.

By doing so, at the end of this process, all mounted endpoints will inherit all the executed methods within the Grape::API scope.

[grape-bot]

	1 Warning
⚠️	There're library changes, but not tests. That's OK as long as you're refactoring existing code.

Generated by 🚫 Danger

[dblock]

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[dblock]

Given that this broke no specs (impressive) I say we merge, thank you! Want to rebase CHANGELOG and potentially edit my nit?

[jcagarcia]

Given that this broke no specs (impressive) I say we merge, thank you! Want to rebase CHANGELOG and potentially edit my nit?

I've just rebased and applied your suggestions! :) Happy to help!