Make text based enum as Derive macro

[Kilerd]

currently sqlx only support enum defined in postgres, but it's not convenient for those "enum" in rust but stored as text/varchar in postgres, what I call as TextEnum, this trait should be derived via proc macro.

we do have a version of declare macro

macro_rules! as_sql_text {
    ($ident:ident) => {
        impl ::sqlx::Type<::sqlx::Postgres> for $ident {
            fn type_info() -> ::sqlx::postgres::PgTypeInfo {
                ::sqlx::postgres::PgTypeInfo::with_oid(1043)
            }
        }

        impl sqlx::Decode<'_, ::sqlx::Postgres> for $ident {
            fn decode(
                value: <::sqlx::Postgres as ::sqlx::database::HasValueRef<'_>>::ValueRef,
            ) -> Result<Self, ::sqlx::error::BoxDynError> {
                use std::str::FromStr;
                let value = <&str as ::sqlx::Decode<::sqlx::Postgres>>::decode(value)?;
                Ok(Self::from_str(value)?)
            }
        }

        impl sqlx::Encode<'_, ::sqlx::Postgres> for $ident {
            fn encode_by_ref(
                &self, buf: &mut <::sqlx::Postgres as ::sqlx::database::HasArguments<'_>>::ArgumentBuffer,
            ) -> ::sqlx::encode::IsNull {
                let x: &str = self.as_ref();
                <&str as ::sqlx::Encode<::sqlx::Postgres>>::encode_by_ref(&x, buf)
            }
        }
    };
}