fix: add supportsArrays to memory and mongodb adapters (#6984)

packages/better-auth/src/adapters/memory-adapter/memory-adapter.ts

@@ -26,6 +26,7 @@ export const memoryAdapter = (
 			adapterName: "Memory Adapter",
 			usePlural: false,
 			debugLogs: config?.debugLogs || false,
+			supportsArrays: true,
 			customTransformInput(props) {
 				const useNumberId =
 					props.options.advanced?.database?.useNumberId ||

packages/better-auth/src/adapters/mongodb-adapter/mongodb-adapter.ts

@@ -560,6 +560,7 @@ export const mongodbAdapter = (
 			mapKeysTransformOutput: {
 				_id: "id",
 			},
+			supportsArrays: true,
 			supportsNumericIds: false,
 			transaction:
 				config?.client && (config?.transaction ?? true)

packages/better-auth/src/context/__snapshots__/create-context.test.ts.snap

@@ -20,7 +20,7 @@ exports[`base context creation > should match config 1`] = `
         "disableTransformInput": false,
         "disableTransformJoin": false,
         "disableTransformOutput": false,
-        "supportsArrays": false,
+        "supportsArrays": true,
         "supportsBooleans": true,
         "supportsDates": true,
         "supportsJSON": false,