feat(codgen): Allow hiding SeaORM specific traits behind features

[AaronDewes]

This PR makes it possible to set a --sea-orm-feature flag that makes generated code not depend on sea-orm unless that feature is enabled.

This allows having just one set of generated files that can be used on frontend and backend for shared types. The --frontend-format flag previously required creating different files.

---

This PR currently lacks tests. Before creating tests, I wanted to open this draft to see if this is even a feature you want or if it's something you wouldn't merge anyway.

PR Info

New Features

• In codegen, allow making any SeaORM-related code only available with a feature enabled.

Bug Fixes

None

Breaking Changes

None

Changes

None

[tyt2y3]

interesting, can you give an example what the generated entity looks like?

[AaronDewes]

interesting, can you give an example what the generated entity looks like?

Here's an example from a project where I'm using this with Leptos (--sea-orm-feature ssr):

//! `SeaORM` Entity, @generated by sea-orm-codegen 2.0

#[cfg(feature = "ssr")]
use sea_orm::entity::prelude::*;
use serde::{Deserialize, Serialize};

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
#[cfg_attr(feature = "ssr", derive(DeriveEntityModel))]
#[cfg_attr(feature = "ssr", sea_orm(table_name = "teams"))]
pub struct Model {
    #[cfg_attr(feature = "ssr", sea_orm(primary_key))]
    pub id: i32,
    pub name: String,
    pub org_id: i32,
}

#[derive(Copy, Clone, Debug)]
#[cfg_attr(feature = "ssr", derive(EnumIter, DeriveRelation))]
pub enum Relation {
    #[cfg_attr(feature = "ssr", sea_orm(has_many = "super::apps::Entity"))]
    Apps,
    #[cfg_attr(
        feature = "ssr",
        sea_orm(
            belongs_to = "super::organizations::Entity",
            from = "Column::OrgId",
            to = "super::organizations::Column::Id",
            on_update = "NoAction",
            on_delete = "Cascade",
        )
    )]
    Organizations,
    #[cfg_attr(feature = "ssr", sea_orm(has_many = "super::team_memberships::Entity"))]
    TeamMemberships,
}

#[cfg(feature = "ssr")]
impl Related<super::apps::Entity> for Entity {
    fn to() -> RelationDef {
        Relation::Apps.def()
    }
}

#[cfg(feature = "ssr")]
impl Related<super::organizations::Entity> for Entity {
    fn to() -> RelationDef {
        Relation::Organizations.def()
    }
}

#[cfg(feature = "ssr")]
impl Related<super::team_memberships::Entity> for Entity {
    fn to() -> RelationDef {
        Relation::TeamMemberships.def()
    }
}

#[cfg(feature = "ssr")]
#[cfg(feature = "ssr")]
impl ActiveModelBehavior for ActiveModel {}

(This is the compact format, I will fix the duplicate cfg in the last block later)