GAX: log gRPC endpoint and RPC being called in debug logging

[bshaffer]

Separate from #9255 because this is a high-priority item

It doesn't seem like gRPC is logging the URL, nor the RPC being called. This may also be the case for REST. The endpoint/RPC being called is critical information to the debugging path.

[bshaffer]

It seems that maybe this has to do with the different log levels, although this also requires some investigation, as our documentation in https://github.com/googleapis/google-cloud-php/blob/main/DEBUG.md does not mention log levels.

So there are two issues I see here:

1. That the RPC name isn't being logged by default
2. that log levels are either not documented or not properly implemented.

If log levels aren't implemented at all, that seems OK. But the issue here seems to be that they're either implemented and not documented, or not properly implemented.

[bshaffer]

The gRPC "name" is now being logged: https://github.com/googleapis/gax-php/commits/main/

Is the endpoint also being logged @Hectorhammett ? If not, we should add it as well!

[Hectorhammett]

@bshaffer We do log the request.url for rest requests. Unless I am missing something, I believe it is what we need:

{
    "timestamp": "2025-09-22T18:11:43+00:00",
    "severity": "DEBUG",
    "processId": 1410636,
    "requestId": 3258552877,
    "jsonPayload": {
        "request.method": "POST",
        "request.url": "https://translate.googleapis.com/v3/projects/<PROJECT>:translateText?%24alt=json%3Benum-encoding%3Dint",
        "request.headers": {
            "Host": [
                "translate.googleapis.com"
            ],
            "Content-Type": [
                "application/json"
            ],
            "x-goog-api-client": [
                "gl-php/8.4.11 gapic/1.21.0 gax/1.37.0 grpc/1.71.0 rest/1.37.0 pb/+n"
            ],
            "User-Agent": [
                "gcloud-php-new/1.21.0"
            ],
            "X-Goog-User-Project": [
                "<PROJECT>"
            ],
            "x-goog-request-params": [
                "parent=projects%<PROJECT>"
            ],
            "authorization": [
                "****"
        },
        "request.payload": "{\"contents\":[\"こんにちは\"],\"targetLanguageCode\":\"en-US\",\"parent\":\"projects\\/<PROJECT>\"}"
    }
}

[bshaffer]

@Hectorhammett I'm asking specifically about for grpc requests... It's not the request URI, it's the grpc endpoint. The rpc name alone doesn't quite tell the whole picture