[RFC] Do not force to use annotations for Sylius project

[Zales0123]

I open this PR as a base for a discussion about default orm mapping in Sylius-Standard.

Right now we have all Sylius entities extended by default in src/Entity/ directory and mapped with annotations mapping - which is correct and useful, as we have no better option to extend Sylius entities in plugins than providing a trait with new properties, including their mapping. So with such a configuration installing a plugin and extending a Sylius entity is quite hassle-free.

HOWEVER

I, personally, feel bad that I'm a little bit forced to use annotations (I really prefer yml or, even better, xml mapping). I know, I'm not the only one, even though there are not so many of us nowadays 🏝 👴 When I create my own, new resource, in src/Entity/ directory, I'm not able to change the mapping type that I hate, without changing it for all other entities. I was struggling with this issue, as I don't want to force anyone to follow my rules, but on the other hand, I don't want to be forced to anything neither 🚀 Moreover, a doctrine mapping configuration is not so smart and we cannot define any rule like "use this mapping or, if it's not defined, use this instead" 😢 The only way to differentiate mappings is to separate entities into subdirectories and configure mapping for them.

As a first proposal, I wanted to move all Sylius entities to src/Entity/Sylius and create another src/Entity/Main directory with different configurations. I found it kinda weird, so I propose a separate configuration for each pack of entities and another one for a src/Entity/Main (name to be refactored), as a directory for custom entities.

I don't know is it the best solution. More, I don't even know if maybe it's my imagined problem 😄 But I would love to see an opinion of others @Sylius/core-team members and, of course, from our beloved community 🎉

Live long and prosper 🖖 ☮️

[loevgaard]

Better names: App, Custom, Application

[loevgaard]

Regarding the actual problem I always use XML in bundles/plugins (which I make a lot of :D) so I am also a big fan of XML, but I am also a big fan of annotations within applications. It's very easy to read, and if I want to use third party plugins they will usually provide an annotated trait, which also makes it very easy.

But I don't see anything wrong with this PR. It gives the flexibility you are looking for at least :)

[Ferror]

@Zales0123 Could you decide to kill or make this feature work? It's been 3 years and I don't see much activity here 😄