macros: add support for Postgres + BigDecimal

sqlx-core/src/postgres/types/mod.rs

@@ -62,6 +62,8 @@ impl PgTypeInfo {
         match self.id {
             TypeId::DATE | TypeId::TIME | TypeId::TIMESTAMP | TypeId::TIMESTAMPTZ => Some("chrono"),
             TypeId::UUID => Some("uuid"),
+            // we can support decoding `PgNumeric` but it's decidedly less useful to the layman
+            TypeId::NUMERIC => Some("bigdecimal"),
             _ => None,
         }
     }

sqlx-macros/src/database/postgres.rs

@@ -25,6 +25,9 @@ impl_database_ext! {
 
         #[cfg(feature = "chrono")]
         sqlx::types::chrono::DateTime<sqlx::types::chrono::Utc> | sqlx::types::chrono::DateTime<_>,
+
+        #[cfg(feature = "bigdecimal")]
+        sqlx::types::BigDecimal
     },
     ParamChecking::Strong,
     feature-types: info => info.type_feature_gate(),