feat(api): port discord/callback to rust

lib/models/src/_util.rs

@@ -0,0 +1,35 @@
+// postgres enums created in c# pluralkit implementations are "fake", i.e. they
+// are actually ints in the database rather than postgres enums, because dapper
+// does not support postgres enums
+// here, we add some impls to support this kind of enum in sqlx
+// there is probably a better way to do this, but works for now.
+// note: caller needs to implement From<i32> for their type
+macro_rules! fake_enum_impls {
+    ($n:ident) => {
+        impl Type<Postgres> for $n {
+            fn type_info() -> PgTypeInfo {
+                PgTypeInfo::with_name("INT4")
+            }
+        }
+
+        impl From<$n> for i32 {
+            fn from(enum_value: $n) -> Self {
+                enum_value as i32
+            }
+        }
+
+        impl<'r, DB: Database> Decode<'r, DB> for $n
+        where
+            i32: Decode<'r, DB>,
+        {
+            fn decode(
+                value: <DB as Database>::ValueRef<'r>,
+            ) -> Result<Self, Box<dyn Error + 'static + Send + Sync>> {
+                let value = <i32 as Decode<DB>>::decode(value)?;
+                Ok(Self::from(value))
+            }
+        }
+    };
+}
+
+pub(crate) use fake_enum_impls;