Allow schema caching per server when using a common base schema

[darvanen]

I am NOT by any means suggesting this at the fix approach, it merely shows where the problem lies so a discussion can be had regarding how to fix it.
Updated to a viable patch, though there are other ways we could approach it.

[darvanen]

See #1223 for initial notes

[darvanen]

I'm sorry, I went to try and create a test to demonstrate this but it's completely beyond me.

[darvanen]

Ok, now this PR contains a potential fix using a setter on the plugin to provide the server ID.

We could probably also do it by putting another key on the configuration that gets passed to the plugin but this seemed safer to me.

[darvanen]

Alright I give up. The last test failure is a conflict between PHPStan and phpcs

PHPStan:

 ------ ------------------------------------------------------------------ 
  Line   src/Plugin/SchemaPluginInterface.php                              
 ------ ------------------------------------------------------------------ 
  23     PHPDoc tag @param has invalid value (string                       
           The machine name of the server using this plugin.): Unexpected  
         token "\n   * ", expected variable at offset 84                   
 ------ ------------------------------------------------------------------ 

phpcs:

FILE: ...odules/graphql/src/Plugin/GraphQL/Schema/SdlSchemaPluginBase.php
----------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
----------------------------------------------------------------------
 47 | ERROR | [x] Do not append variable name "$serverId" to the type
    |       |     declaration in a member variable comment
----------------------------------------------------------------------
PHPCBF CAN FIX THE 1 MARKED SNIFF VIOLATIONS AUTOMATICALLY
----------------------------------------------------------------------

[pfrenssen]

Instead of using a setter to configure the server ID, I'm wondering if it wouldn't be better to make the plugin configurable by implementing ConfigurableInterface. In fact, both schema plugins we ship are already configurable (but the base class SdlSchemaPluginBase isn't, and changing this would be a B/C break).

[pfrenssen]

This assumes that the setter has always been called, but it might not have been, and $this->serverId might be NULL.

Probably using a setter is not the best approach. Since the server ID is required for the plugin to work in the current it is essential that the setter is always called. The setter is not part of the SchemaPluginInterface and it also should not be, since it is not essential for all schema plugins, only for the ones that use caching.

Maybe we can add a server_name key to the standard plugin configuration and check that this is populated in the plugin constructor? That would also enable us to gracefully introduce this change. We can emit a deprecation warning if it is missing.