Remove paragraph about doctrine mapping override

[l-vo]

Hello,

I would suggest to remove the paragraph about mapping override because it doesn't work in all cases.

I read the related PR (#10053) and the issue (#7076) which motivated it. The example in the issue works only because auto_mapping is set to true (auto_mapping: true allows to find definitions in `Resources/config/doctrine/*.orm.{xml, yml, php} of all the bundles even if nothing is declared in the bundles).

From the POV of the bundle , it's IMHO not a good practice to rely on app auto_mapping configuration (the trend for sf4 and sf5 is to rely on configurations over conventions).

So when bundle mapping rely on the dedicated compiler pass (example here) and not on auto_mapping app configuration , the mapping definition file in the compiler pass (from the bundle) overrides the mapping definition file defined in the application.

[javiereguiluz]

I don't know if we should remove this paragraph or not (some Doctrine experts will need to help us here). But if we remove it ... then we need to add some content saying that it's not possible to override that config. The current docs say "you can do XXX" ... so if it's not possible, we should say "you CANNOT do XXX" instead of deleting the original phrase.

[l-vo]

@javiereguiluz thank you for you feedback. I tweaked the update to underline the can/cannot idea (actually, the second paragraph explains it's possible via mapped superclasses, so I replaced "cannot" by "can only"). Now let's wait for Doctrine experts feedback :)

[javiereguiluz]

Thanks Laurent! Merged.

[l-vo]

@javiereguiluz great :) Have you had any confirmation from a Doctrine expert ?

[javiereguiluz]

I haven't, but we need to be more proactive when merging things because we have tons of pending things to do.

[l-vo]

Ok I understand, thank you. I tested what I wrote anyway.