Short summary (3-5 sentences) describing the issue.

Assemblies affected

See details at: CustomUriFunctions should not be static or irreversible (#821)

Additional detail

• One proposal: We can create an annotation to hold the static mapping and attach it to the corresponding 'EdmModel'. So, for different Edm model, we have different custom functions mapping and avoid conflict and static globally.

• Another: We can create the CustomUriFunction Provider through the DI and customer can use it to provide the "Customized" functions.