fix: enable the comment in model config files.

Casbin.UnitTest/examples/basic_model.conf

@@ -1,11 +1,11 @@
 [request_definition]
-r = sub, obj, act
+r = sub, obj, act    ### The following text is a test for comment in model config.
 
 [policy_definition]
-p = sub, obj, act
+p = sub, obj, act   #This is a comment, splited by a comma
 
 [policy_effect]
-e = some(where (p.eft == allow))
+e = some(where (p.eft == allow))# Comment
 
 [matchers]
-m = r.sub == p.sub && r.obj == p.obj && r.act == p.act
+m = r.sub == p.sub && r.obj == p.obj && r.act == p.act  # Comment, another comment ###

Casbin/Model/DefaultModel.cs

@@ -107,10 +107,11 @@ public bool AddDef(string section, string key, string value)
                 return false;
             }
 
+            int commentStartIdx = value.IndexOf(PermConstants.PolicyCommentChar);
             var assertion = new Assertion
             {
                 Key = key,
-                Value = value
+                Value = commentStartIdx == -1 ? value : value.Remove(commentStartIdx)
             };
 
             if (section.Equals(PermConstants.Section.RequestSection)

Casbin/PermConstants.cs

@@ -4,6 +4,7 @@ public static class PermConstants
     {
         public const char PolicySeparatorChar = ',';
         public const string PolicySeparatorString = ", "; // include a white space
+        public const char PolicyCommentChar = '#';
 
         public const string DefaultRequestType = "r";
         public const string RequestType2 = "r2";