[MM-20353] Change KVSetWithOptions to accept a byte slice (#13213)

* Drop EncodeJSON from PluginKVSetOptions

* Add unit tests for KVSetWithOptions with nil values

plugin/client_rpc_generated.go

@@ -3698,7 +3698,7 @@ func (s *apiRPCServer) KVCompareAndDelete(args *Z_KVCompareAndDeleteArgs, return
 
 type Z_KVSetWithOptionsArgs struct {
 	A string
-	B interface{}
+	B []byte
 	C model.PluginKVSetOptions
 }
 
@@ -3707,8 +3707,8 @@ type Z_KVSetWithOptionsReturns struct {
 	B *model.AppError
 }
 
-func (g *apiRPCClient) KVSetWithOptions(key string, newValue interface{}, options model.PluginKVSetOptions) (bool, *model.AppError) {
-	_args := &Z_KVSetWithOptionsArgs{key, newValue, options}
+func (g *apiRPCClient) KVSetWithOptions(key string, value []byte, options model.PluginKVSetOptions) (bool, *model.AppError) {
+	_args := &Z_KVSetWithOptionsArgs{key, value, options}
 	_returns := &Z_KVSetWithOptionsReturns{}
 	if err := g.client.Call("Plugin.KVSetWithOptions", _args, _returns); err != nil {
 		log.Printf("RPC call to KVSetWithOptions API failed: %s", err.Error())
@@ -3718,7 +3718,7 @@ func (g *apiRPCClient) KVSetWithOptions(key string, newValue interface{}, option
 
 func (s *apiRPCServer) KVSetWithOptions(args *Z_KVSetWithOptionsArgs, returns *Z_KVSetWithOptionsReturns) error {
 	if hook, ok := s.impl.(interface {
-		KVSetWithOptions(key string, newValue interface{}, options model.PluginKVSetOptions) (bool, *model.AppError)
+		KVSetWithOptions(key string, value []byte, options model.PluginKVSetOptions) (bool, *model.AppError)
 	}); ok {
 		returns.A, returns.B = hook.KVSetWithOptions(args.A, args.B, args.C)
 	} else {