Add much more GraphQL schema validation

[ra0x3]

• We have a GraphQLSchemaValidator in fuel_indexer_lib::graphql::validator
• This object is responsible for making sure users aren't writing GraphQL schema that will throw the indexer in a weird state (whether at compile time or runtime)
• We need to add a lot more rules to this validator, since currently, users can do some wacky stuff that puts the service into weird states

Some rules I can think of off the top of my head are:

• No nested lists in schema
• No nested foreign key references
• All id field names must be of ID
• Virtual types (tagged with a @virtual directive) can't have id: ID fields
• Can't use reserved names
• Can't have TypeDefinition with too long of name
• Can't have FieldDefinition with too long of a name
• Can't use unique directive @unique on a foreign key field
• Can't use @unique directive on any TypeDefinition that is already @virtual
• If using ::new() apparently can't include a u64 foreign key as the first arg?
• Within the context of list types, that any Vec that could possibly be empty is typed as [Foo!] or [Foo] (where the outer list is optional)
• Can't have a TypeDefinition with many-to-many relationships that exceed MAX_MANY_TO_MANY_RELATIONSHIPS = 10
  • Defined in this PR enhancement: implement many-to-many relationships #1140
• Can't have a FieldDefinition that is a many-to-many relationship, where the FK is explicit (i.e., the FK points to anything other than an ID type on the child TypeDefintion)

(We can add to this list as we think of more things)

Additional context:

• These rules should also be clearly document in the book