[receiver/googlecloudpubsubpush] Add telemetry metrics (open-telemetry#44422)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Add telemetry metrics.

<!--Describe what testing was performed and which tests were added.-->
#### Testing

Unit test added.

<!--Describe the documentation added.-->
#### Documentation

Documentation updated.

---------

Co-authored-by: Christos Markou <[email protected]>

Author: constanca-m

.chloggen/googlecloudpubsubpush-add-telemetry.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/filelog)
+component: receiver/googlecloudpubsubpush
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add telemetry metrics to the component.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [44422]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

receiver/googlecloudpubsubpushreceiver/documentation.md

@@ -0,0 +1,43 @@
+[comment]: <> (Code generated by mdatagen. DO NOT EDIT.)
+
+# googlecloudpubsubpush
+
+## Internal Telemetry
+
+The following telemetry is emitted by this component.
+
+### otelcol_gcp.pubsub.input.uncompressed.size
+
+Size of uncompressed incoming log data in bytes (either direct Pub/Sub message payloads or GCS file content retrieved from event notifications). [Development]
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| By | Histogram | Double | Development |
+
+#### Attributes
+
+| Name | Description | Values |
+| ---- | ----------- | ------ |
+| gcp.gcs.bucket.name | Bucket name. | Any Str |
+
+### otelcol_http.server.request.active.count
+
+Number of active requests. [Development]
+
+| Unit | Metric Type | Value Type | Monotonic | Stability |
+| ---- | ----------- | ---------- | --------- | --------- |
+| {count} | Sum | Int | false | Development |
+
+### otelcol_http.server.request.duration
+
+Duration of requests in seconds. [Development]
+
+| Unit | Metric Type | Value Type | Stability |
+| ---- | ----------- | ---------- | --------- |
+| s | Histogram | Double | Development |
+
+#### Attributes
+
+| Name | Description | Values |
+| ---- | ----------- | ------ |
+| http.response.status_code | HTTP response status code. | Any Int |

receiver/googlecloudpubsubpushreceiver/factory.go

@@ -27,5 +27,5 @@ func createLogsReceiver(
 	cfg component.Config,
 	nextLogs consumer.Logs,
 ) (receiver.Logs, error) {
-	return newPubSubPushReceiver(cfg.(*Config), set, nextLogs), nil
+	return newPubSubPushReceiver(cfg.(*Config), set, nextLogs)
 }

receiver/googlecloudpubsubpushreceiver/go.mod

@@ -23,6 +23,10 @@ require (
 	go.opentelemetry.io/collector/pdata v1.46.1-0.20251120204106-2e9c82787618
 	go.opentelemetry.io/collector/receiver v1.46.1-0.20251120204106-2e9c82787618
 	go.opentelemetry.io/collector/receiver/receivertest v0.140.1-0.20251120204106-2e9c82787618
+	go.opentelemetry.io/otel v1.38.0
+	go.opentelemetry.io/otel/metric v1.38.0
+	go.opentelemetry.io/otel/sdk/metric v1.38.0
+	go.opentelemetry.io/otel/trace v1.38.0
 	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.27.0
 )
@@ -87,11 +91,7 @@ require (
 	go.opentelemetry.io/contrib/detectors/gcp v1.38.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.61.0 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.63.0 // indirect
-	go.opentelemetry.io/otel v1.38.0 // indirect
-	go.opentelemetry.io/otel/metric v1.38.0 // indirect
 	go.opentelemetry.io/otel/sdk v1.38.0 // indirect
-	go.opentelemetry.io/otel/sdk/metric v1.38.0 // indirect
-	go.opentelemetry.io/otel/trace v1.38.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/crypto v0.45.0 // indirect