Switch to use reserved mypy-protobuf extension option numbers (#403)

Fixes #396

Author: nipunn1313

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## Upcoming
 
 - Mark messages as @typing.final
+- Switch to use the reserved mypy-protobuf extension option numbers https://github.com/protocolbuffers/protobuf/blob/main/docs/options.md
 
 ## 3.3.0
 

mypy_protobuf/extensions_pb2.py

@@ -16,10 +16,10 @@ message FieldOptions {
 
 extend google.protobuf.FieldOptions {
     // Custom field options from mypy-protobuf
-    FieldOptions options = 60004;
+    FieldOptions options = 1154;
 
     // Legacy fields. Prefer to use ones within `options` instead.
-    string casttype = 60000 [deprecated = true];
-    string keytype = 60002 [deprecated = true];
-    string valuetype = 60003 [deprecated = true];
+    string casttype = 1151 [deprecated = true];
+    string keytype = 1152 [deprecated = true];
+    string valuetype = 1153 [deprecated = true];
 }