(Maybe?) Generate PHP client

[achaphiv]

Our caller uses PHP, so perhaps we should create a client stub for PHP?

There's a plugin already. It's just not supported by default with the generated SDKs.

Buf generated SDKs

PHP buf plugin

TODO

• [ ] Figure out where to deploy this (note that github packages doesn't work)
• [ ] Generate php client via github workflow

[achaphiv]

This is not necessary. We went with the grpc-gateway project, which implements a proxy server written in go.