For Wikibases with federation enabled to Wikidata.org

• Automatically alter entitysources configuration to use Wikidata.org values for properties
• No intervention from the user necessary

T253868 includes some details about this entity sources config (and it is still being discussed in matter most)

The config that we would look for to assume that wikidata.org is being referred to, and thus set this entity sources config would be:

'federatedPropertiesSourceScriptUrl' => 'https://www.wikidata.org/w/',

Code pointers:
WikibaseRepo::getEntitySourceDefinitionsFromSettings creates the definitions object from config for repo. This will likely need to know somehow if it should add our fed props entity source. This could be done by altering the config parser, or altering the config we pass into the parser.
EntitySourceDefinitionsConfigParser is the "modern" config parser that we want to alter.
It is fine to not support/change EntitySourceDefinitionsLegacyRepoSettingsParser (as that is not the default any more and will be removed soon)