adding docs and supportedClientDataClasses

src/darwin/Framework/CHIP/MTRDevice.h

@@ -243,12 +243,20 @@ typedef NS_ENUM(NSUInteger, MTRDeviceState) {
 /**
  *
  * This set of functions allows clients to store metadata for either an entire device or for a specific endpoint.
- * Values must conform to NSSecureCoding
  *
  * Notes:
  *   • Client data will be removed automatically when devices are deleted from the fabric
+ *   • Supported client data object types are currently only:
+ *         NSData, NSString, NSArray, NSDictionary, NSNumber
  */
 
+/**
+ *
+ * List of all client data types supported
+ *
+ */
+- (NSArray *)supportedClientDataClasses MTR_NEWLY_AVAILABLE;
+
 /**
  *
  * List of all client data keys stored

src/darwin/Framework/CHIP/MTRDevice.mm

@@ -1723,6 +1723,10 @@ - (MTRBaseDevice *)newBaseDevice
 
 // Client Metadata Storage
 
+- (NSArray *)supportedClientDataClasses {
+    return @[[NSData class], [NSString class], [NSNumber class], [NSDictionary class], [NSArray class]];
+}
+
 - (NSArray * _Nullable)clientDataKeys {
     return [self.temporaryMetaDataCache allKeys];
 }
@@ -1736,6 +1740,8 @@ - (NSArray * _Nullable)clientDataKeys {
 
 - (void)setClientDataForKey:(NSString *)key value:(id<NSSecureCoding>)value
 {
+    // TODO: Check supported data types, and also if they conform to NSSecureCoding, when we store these
+
     if ( key == nil || value == nil ) return;
 
     if (self.temporaryMetaDataCache == nil) {