Added group attribute to stop router from merging exception-handlers (issue: #573)

- Added new mergeExceptionHandlers attribute to stop router from merging exception-handlers.
- RouteGroup: Added setMergeExceptionHandlers and getMergeExceptionHandlers methods.
- IRouteGroup: Added setMergeExceptionHandlers and getMergeExceptionHandlers method.
- Updated documentation to reflect changes.
- Added unit-tests.

src/Pecee/SimpleRouter/Route/RouteGroup.php

@@ -12,6 +12,7 @@ class RouteGroup extends Route implements IGroupRoute
     protected $name;
     protected $domains = [];
     protected $exceptionHandlers = [];
+    protected $mergeExceptionHandlers = true;
 
     /**
      * Method called to check if a domain matches
@@ -36,6 +37,7 @@ class RouteGroup extends Route implements IGroupRoute
 
             if ($parameters !== null && count($parameters) !== 0) {
                 $this->parameters = $parameters;
+
                 return true;
             }
         }
@@ -174,6 +176,29 @@ class RouteGroup extends Route implements IGroupRoute
         return $this->prefix;
     }
 
+    /**
+     * When enabled group will overwrite any existing exception-handlers.
+     *
+     * @param bool $merge
+     * @return static
+     */
+    public function setMergeExceptionHandlers(bool $merge): self
+    {
+        $this->mergeExceptionHandlers = $merge;
+
+        return $this;
+    }
+
+    /**
+     * Returns true if group should overwrite existing exception-handlers.
+     *
+     * @return bool
+     */
+    public function getMergeExceptionHandlers(): bool
+    {
+        return $this->mergeExceptionHandlers;
+    }
+
     /**
      * Merge with information from another route.
      *
@@ -187,6 +212,10 @@ class RouteGroup extends Route implements IGroupRoute
             $this->setPrefix($settings['prefix'] . $this->prefix);
         }
 
+        if (isset($settings['mergeExceptionHandlers']) === true) {
+            $this->setMergeExceptionHandlers($settings['mergeExceptionHandlers']);
+        }
+
         if ($merge === false && isset($settings['exceptionHandler']) === true) {
             $this->setExceptionHandlers((array)$settings['exceptionHandler']);
         }