Generate doc comments based on table/column comment

[naskya]

Since auto-generated files are not intended to be edited, generated Models inevitably lack documentation. It would be nice if sea-orm-codegen would write doc comments based on table/column comments.

Example schema and generated code:

CREATE TABLE "user" (
    "id" bigserial PRIMARY KEY,
    "name" varchar(255) NOT NULL,
    "foo" varchar(255) NOT NULL
);

COMMENT ON TABLE "user" IS 'User data';
COMMENT ON COLUMN "user"."id" IS 'The user ID.';
COMMENT ON COLUMN "user"."name" IS 'The name of this user.';
COMMENT ON COLUMN "user"."foo" IS 'This is something.';

#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
#[sea_orm(table_name = "user")]
/// User data
pub struct Model {
    #[sea_orm(primary_key)]
    /// The user ID.
    pub id: i64,
    /// The name of this user.
    pub name: String,
    /// This is something.
    pub foo: String,
}

// or

#[derive(Clone, Debug, PartialEq, DeriveEntityModel, Eq)]
#[sea_orm(table_name = "user")]
#[doc = "User data"]
pub struct Model {
    #[sea_orm(primary_key)]
    #[doc = "The user ID."]
    pub id: i64,
    #[doc = "The name of this user."]
    pub name: String,
    #[doc = "This is something."]
    pub foo: String,
}

[baraknaveh]

See also: #2352. Feel free to merge the two discussions if you see fit.