Emit `isAbstract` decorator option

By default, TypeGraphQL Prisma generator aims to work with newest release of TypeGraphQL. However, for backward compatibility reasons, there are some config options introduced.

One of such options is emitIsAbstract generator option:

generator typegraphql {
  provider       = "typegraphql-prisma"
  emitIsAbstract = true
}

When this option is set to true, it generates isAbstract: true decorator option for @ObjectType (models, outputs) and @InputType classes:

@TypeGraphQL.ObjectType("Post", {
  isAbstract: true,
})
export class Post {
  @TypeGraphQL.Field(_type => TypeGraphQL.ID, {
    nullable: false,
  })
  uuid!: string;

  // ...
}

This decorator option prevents from emitting those types in GraphQL schema if they are not referenced directly in the other types consumed by resolvers. It only matters if you use the resolvers auto discovery feature (e.g. resolvers: ["./src/**/*.resolver.ts"]), that was supported in TypeGraphQL up to the v2.0.0-beta.1 and removed in newer releases.

Hence this option is set to false by default, so if you still using some old version of TypeGraphQL together with resolvers auto discovery feature, you need to enable emitIsAbstract = true in your Prisma schema.