Remove the entity default index of the identity server module.

[maliming]

Resolve #2451
based on https://github.com/IdentityServer/IdentityServer4/blob/master/src/EntityFramework.Storage/src/Extensions/ModelBuilderExtensions.cs

Need to add or recreate migrations.

[hikalkan]

@maliming you are removing the primary keys (they are composite PK here) of the tables, not their indexes.

As I see the IDS4 implementation, they defined Id properties to the entities. But our entities has no Id property. We are implementing DDD and these entities are not aggregate roots, so we didn't define an unnecessary Id.

I don't know how to solve the problem. Maybe we need to decrease the total length of the primary keys, or define an Id property for these entities (which will require the code change on the entities and other services). This would be a big breaking change. We can go with the first option if we need.