Some directives should apply to the ID type

[paul-pop]

First and foremost, thank you for this library, it's fantastic and I hope it gets the love it deserves 🙂

I am currently seeing an issue when I try to add certain directives to ID fields:

Failed to instantiate [graphql.schema.GraphQLSchema]: Factory method 'graphQLSchema' threw exception; nested exception is graphql.AssertException: The directive rule '@NotBlank' cannot be placed on elements of type 'ID'"

I think some directives like @NotEmpty, @NotBlank to start off would really help on ID fields. If you want to be extra safe we could even add @Pattern, @Expression, @Size and others later.

If I get the chance I will work on this and raise a PR but currently a bit swamped.

[setchy]

@paul-pop - I got some time this morning and added ID scalar support to @Pattern, @NotEmpty, @NotBlank and @Size. @Expression already supports all types.

PR #24

[setchy]

@bbakerman just wanted to confirm if we close this issue after we've released new versions of 14.x.x and 15.x.x