chore: add reason for cancel call click button (#1577)

Note: Ideally `CancelCallButton` should have been named generically as
`HangupCallButton`, but would be a breaking change so I did not do it
here

packages/react-sdk/src/components/RingingCall/RingingCallControls.tsx

@@ -18,7 +18,10 @@ export const RingingCallControls = () => {
         <>
           <AcceptCallButton disabled={buttonsDisabled} />
           <CancelCallButton
-            onClick={() => call.leave({ reject: true })}
+            onClick={() => {
+              const reason = call.isCreatedByMe ? 'cancel' : 'decline';
+              call.leave({ reject: true, reason });
+            }}
             disabled={buttonsDisabled}
           />
         </>