feat(gax): add StringHttpResponseParser

[whowes]

Currently gax-httpjson includes only one HTTP response parser (ProtoMessageResponseParser) which assumes responses can be parsed into protos.

Resumable upload HTTP operations will return non-proto responses so we'll need a more general response parser to be able to use the existing HTTP stack to talk to the upload service.

[gemini-code-assist]

Code Review

This pull request introduces StringHttpResponseParser along with its unit tests to parse HTTP response bodies directly into UTF-8 strings. The review feedback highlights a potential resource leak in StringHttpResponseParser.java where the Reader object passed to the parse method is not closed, and suggests wrapping it in a try-with-resources block to ensure exception-safe resource management.

[gemini-code-assist]

The Reader passed to parse(Reader, TypeRegistry) is not closed after reading, which can lead to resource leaks. Please wrap the httpContent in a try-with-resources block to ensure it is always closed properly and the implementation is exception-safe.

Suggested change

	public String parse(Reader httpContent, TypeRegistry registry) {
	try {
	return CharStreams.toString(httpContent);
	} catch (IOException e) {
	throw new RestSerializationException("Failed to read response body as string", e);
	}
	}
	@Override
	public String parse(Reader httpContent, TypeRegistry registry) {
	try (Reader reader = httpContent) {
	return CharStreams.toString(reader);
	} catch (IOException e) {
	throw new RestSerializationException("Failed to read response body as string", e);
	}
	}

References

1. When managing closeable resources, ensure they are closed in an exception-safe manner to prevent resource leaks.

[whowes]

Opting to not close here as the caller that passes in the Reader should be responsible for managing its lifecycle

[sonarqubecloud]

Quality Gate passed for 'gapic-generator-java-root'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate failed for 'gapic-generator-java-root'

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud