Extension based inject_graphql

[billy1624]

I saw we're using some magic to inject graphql derives to Model, Relation and ActiveEnum. It's not future proof and depends heavily on the output of SeaORM codegen. Let say, the sea_orm attribute comes before derive, then the inject_graphql code will fail.

// `inject_graphql` expect this as the input
#[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
#[sea_orm(table_name = "actor")]
pub struct Model {
    #[sea_orm(primary_key)]
    pub actor_id: u16,
    pub first_name: String,
    pub last_name: String,
    pub last_update: DateTimeUtc,
}

// How about this?
#[sea_orm(table_name = "actor")]
#[derive(Clone, Debug, PartialEq, DeriveEntityModel)]
pub struct Model {
    #[sea_orm(primary_key)]
    pub actor_id: u16,
    pub first_name: String,
    pub last_name: String,
    pub last_update: DateTimeUtc,
}

We can provide extension inside SeaORM codegen. For example, EntityWriterContext can store a Option<dyn ExtendModelStructWriter> where we can specify additional derives and attributes for the generated Model. The trait will take some context provided by the SeaORM codegen. Feel free to rename it or even take the context as &EntityWriterContext.

pub trait ExtendModelStructWriter {
    fn expended_model_extra_derives(entity: &Entity, with_serde: &WithSerde, date_time_crate: &DateTimeCrate) -> TokenStream;

    fn compact_model_extra_attributes(entity: &Entity, with_serde: &WithSerde, date_time_crate: &DateTimeCrate, schema_name: &Option<String>) -> TokenStream;
}