Macro impl_opaque_keys

macro_rules! impl_opaque_keys {
    {
		$( #[ $attr:meta ] )*
		pub struct $name:ident {
			$(
				$( #[ $inner_attr:meta ] )*
				pub $field:ident: $type:ty,
			)*
		}
	} => { ... };
}

Implement OpaqueKeys for a described struct.

Every field type must implement BoundToRuntimeAppPublic. KeyTypeIdProviders is set to the types given as fields.

use sp_runtime::{
	impl_opaque_keys, KeyTypeId, BoundToRuntimeAppPublic, app_crypto::{sr25519, ed25519}
};

pub struct KeyModule;
impl BoundToRuntimeAppPublic for KeyModule { type Public = ed25519::AppPublic; }

pub struct KeyModule2;
impl BoundToRuntimeAppPublic for KeyModule2 { type Public = sr25519::AppPublic; }

impl_opaque_keys! {
	pub struct Keys {
		pub key_module: KeyModule,
		pub key_module2: KeyModule2,
	}
}