refactor: switch to subsystem loggers for HTTP logging

[ctreatma]

This addresses a linting issue that was bypassed in #736 to constrain the scope of that PR. The logging transport we were previously using for HTTP clients is deprecated, but the new Terraform logging plugin is more context-aware and requires--or at least enables--specifying separate subsystems for each provider component that will write logs.

This adds a new HTTPLoggingTransport type that encapsulates the logic of creating a subsystem HTTP logging transport, ensuring the necessary subsystem exists in any relevant HTTP request context, and masking any sensitive values in the request.

The Config type is updated to create a separate HTTPLoggingTransport for each API client. For now, the log level for all of the new transports is wired up to the TF_LOG environment variable. This matches the previous behavior of the deprecated HTTP logging transport.

[ctreatma]

Using TF_LOG to control the log level for all of the new subsystem loggers replicates prior behavior but may not be desirable. Now that we have these loggers in place, we could add support for one or more of TF_LOG_PROVIDER_EQUINIX (to specify log level for the whole provider) or TF_LOG_EQUINIX_<service> (to allow more granular configuration of provider logging).

[ctreatma]

The log format for HTTP logs is different with the new loggers. Previously we would see logs like this:

---[ REQUEST ]---------------------------------------
GET /metal/v1//devices/5f286421-214e-4366-9358-f77a6d3ea4b0?include=project HTTP/1.1
Host: api.equinix.com
User-Agent: HashiCorp Terraform/1.8.1 (+https://www.terraform.io) Terraform Plugin SDK/unknown-version terraform-provider-equinix/dev equinix-sdk-go/0.42.0
Accept: application/json

-----------------------------------------------------
2024/07/23 10:45:45 [DEBUG] Equinix Metal (metal-go) API Response Details:
---[ RESPONSE ]--------------------------------------
HTTP/1.1 200 OK
Content-Length: 19139
Cache-Control: max-age=0, private, must-revalidate
Connection: keep-alive
Content-Type: application/json; charset=utf-8

{
 "id": "5f286421-214e-4366-9358-f77a6d3ea4b0",
 "short_id": "5f286421",
 "hostname": "tfacc-test-device-8858291862441735794",
 "description": "",
 "tags": [
  "8858291862441735794"
 ], ...
}

But the new loggers produce messages like this:

2024-07-23T14:47:34.535-0500 [DEBUG] equinix.Equinix Metal (metal-go): Sending HTTP Request: tf_http_trans_id=bce44d87-fd74-f11e-c4cd-2b90f42d73ab tf_http_req_body="" tf_http_req_version=HTTP/1.1 Host=api.equinix.com tf_http_op_type=request Accept=application/json X-Auth-Token="***" tf_http_req_method=DELETE User-Agent="HashiCorp Terraform/ (+https://www.terraform.io) Terraform Plugin Framework/unknown-version terraform-provider-equinix/dev equinix-sdk-go/0.42.0" tf_http_req_uri=/metal/v1//projects/701296d1-3de0-41fd-8f04-2142bbe1c733 Accept-Encoding=gzip
2024-07-23T14:47:35.160-0500 [DEBUG] equinix.Equinix Metal (metal-go): Received HTTP Response: tf_http_res_body="" X-Xss-Protection="1; mode=block" Cache-Control=no-cache X-Request-Id=3945d28e69a415cd76c5e5d172d75cc1 tf_http_res_status_code=204 X-Content-Type-Options=nosniff tf_http_trans_id=bce44d87-fd74-f11e-c4cd-2b90f42d73ab X-Permitted-Cross-Domain-Policies=none Referrer-Policy=strict-origin-when-cross-origin Date="Tue, 23 Jul 2024 19:47:35 GMT" tf_http_op_type=response tf_http_res_version=HTTP/1.1 X-Frame-Options=SAMEORIGIN X-Download-Options=noopen Connection=keep-alive Strict-Transport-Security="max-age=31536000; includeSubDomains" tf_http_res_status_reason="204 No Content"

[ctreatma]

Another alternative would be to remove the HTTP logging transport entirely and update the Go SDK(s) to enable debug mode in the presence of specific environment variables instead.

[ctreatma]

Looks like we missed a spot in the SDK conversion. This could either be (equinix-sdk-go) to reflect the previous convention of tagging with the SDK name or it could be (metalv1) to align with the fabricClientSubsystem format, in which case perhaps we could remove packetClientSubsystem, since the logs would already include User-Agent to see which requests came from which SDK.

Suggested change

	metalClientSubsystem = "Equinix Metal (metal-go)"
	metalClientSubsystem = "Equinix Metal (equinix-sdk-go)"

[ctreatma]

The new subsystem loggers add support for masking sensitive values, which is nice.