[Routing] allow extending Route attribute

[robmro27]

Q	A
Branch?	5.x
Bug fix?	no
New feature?	no
Deprecations?	no
Tickets
License	MIT
Doc PR

There is probably missed \ReflectionAttribute::IS_INSTANCEOF parameter and because of that Route attribute class could not be extended. This could be used by some popular bundles like FOSRestBundle for example. Right
now it's not possible to add attributes support there like it was before (extending Route Annotation).

[carsonbot]

Hey!

I see that this is your first PR. That is great! Welcome!

Symfony has a contribution guide which I suggest you to read.

In short:

• Always add tests
• Keep backward compatibility (see https://symfony.com/bc).
• Bug fixes must be submitted against the lowest maintained branch where they apply (see https://symfony.com/releases)
• Features and deprecations must be submitted against the 5.x branch.

Review the GitHub status checks of your pull request and try to solve the reported issues. If some tests are failing, try to see if they are failing because of this change.

When two Symfony core team members approve this change, it will be merged and you will become an official Symfony contributor!
If this PR is merged in a lower version branch, it will be merged up to all maintained branches within a few days.

I am going to sit back now and wait for the reviews.

Cheers!

Carsonbot

[robmro27]

Hey thanks for quick check. Is this continuous-integration/appveyor/pr AppVeyor build failed something I should fix somehow ?

[nicolas-grekas]

The failing test is unrelated.

[fabpot]

Thank you @robmro27.