Increase google-protobuf version requirement to 3.21.12+

Earlier versions fail to load the `protovalidate` extension field descriptors with
"field with proto3_optional was not in a oneof (buf.validate.priv.field)".

protocolbuffers/upb#1034

Signed-off-by: Andrew Haines <haines@cerbos.dev>

CHANGELOG.md

@@ -7,6 +7,8 @@
   This makes the API consistent with policy expressions.
   `attributes` is still supported for backwards compatibility, but is now deprecated.
 
+- Increased [`google-protobuf`] version requirement to 3.21.12+ to avoid [failure to load `protovalidate` extension field descriptors](https://github.com/protocolbuffers/upb/pull/1034) ([#159](https://github.com/cerbos/cerbos-sdk-ruby/pull/159))
+
 ### Removed
 
 - Support for Ruby 3.0 ([#158](https://github.com/cerbos/cerbos-sdk-ruby/pull/158))
@@ -75,7 +77,7 @@
 
 ### Changed
 
-- Increased `grpc` version requirement to 1.46+ to avoid [installing a native gem compiled for `x86_64-darwin` on `arm64-darwin`](https://github.com/grpc/grpc/issues/29100) ([#8](https://github.com/cerbos/cerbos-sdk-ruby/pull/8))
+- Increased [`grpc`] version requirement to 1.46+ to avoid [installing a native gem compiled for `x86_64-darwin` on `arm64-darwin`](https://github.com/grpc/grpc/issues/29100) ([#8](https://github.com/cerbos/cerbos-sdk-ruby/pull/8))
 
 ## [0.1.0] - 2022-05-12
 
@@ -93,3 +95,5 @@
 [0.3.0]: https://github.com/cerbos/cerbos-sdk-ruby/compare/v0.2.0...v0.3.0
 [0.2.0]: https://github.com/cerbos/cerbos-sdk-ruby/compare/v0.1.0...v0.2.0
 [0.1.0]: https://github.com/cerbos/cerbos-sdk-ruby/compare/4481009e9dec2e1e6a2df8ea2f828690ceabbefc...v0.1.0
+[`google-protobuf`]: https://rubygems.org/gems/google-protobuf
+[`grpc`]: https://rubygems.org/gems/grpc

Gemfile.lock

@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     cerbos (0.8.0)
-      google-protobuf (~> 3.19)
+      google-protobuf (>= 3.21.12, < 4.0)
       grpc (~> 1.46)
 
 GEM

cerbos.gemspec

@@ -33,5 +33,5 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = ">= 3.1.0"
   spec.add_dependency "grpc", "~> 1.46"
-  spec.add_dependency "google-protobuf", "~> 3.19"
+  spec.add_dependency "google-protobuf", [">= 3.21.12", "< 4.0"]
 end