Reorganize source files of collab::db

* Move all sea_orm tables into a 'tables' module
* Move TestDb into its own file
* Move id types into their own module

crates/collab/src/db/tables/language_server.rs

@@ -0,0 +1,30 @@
+use crate::db::ProjectId;
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
+#[sea_orm(table_name = "language_servers")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub project_id: ProjectId,
+    #[sea_orm(primary_key)]
+    pub id: i64,
+    pub name: String,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(
+        belongs_to = "super::project::Entity",
+        from = "Column::ProjectId",
+        to = "super::project::Column::Id"
+    )]
+    Project,
+}
+
+impl Related<super::project::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Project.def()
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}