Fix RestTemplateInterceptor so that it calls endExceptionally() on exception

[mateuszrzeszutek]

Resolves #2479

I've added a few testing changes in this PR because I wouldn't be able to unit-test my change otherwise:

• implemented a new TraceUtils class in testing-common; contrary to the old one it uses BaseTracer to create spans, so we can now test span suppression;
• added mockito to dependencies.gradle

[laurit]

Maybe we could also test it the same way as we do for other http clients.

import io.opentelemetry.api.GlobalOpenTelemetry
import io.opentelemetry.instrumentation.spring.httpclients.RestTemplateInterceptor
import io.opentelemetry.instrumentation.test.AgentTestTrait
import io.opentelemetry.instrumentation.test.base.HttpClientTest
import org.springframework.http.HttpEntity
import org.springframework.http.HttpHeaders
import org.springframework.http.HttpMethod
import org.springframework.http.client.SimpleClientHttpRequestFactory
import org.springframework.web.client.RestTemplate

class RestTemplateTest extends HttpClientTest implements AgentTestTrait {

  @Override
  int doRequest(String method, URI uri, Map<String, String> headers, Closure callback) {
    SimpleClientHttpRequestFactory clientHttpRequestFactory = new SimpleClientHttpRequestFactory()
    clientHttpRequestFactory.setConnectTimeout(CONNECT_TIMEOUT_MS)
    RestTemplate restTemplate = new RestTemplate(clientHttpRequestFactory)
    RestTemplateInterceptor restTemplateInterceptor = new RestTemplateInterceptor(GlobalOpenTelemetry.get())
    restTemplate.getInterceptors().add(restTemplateInterceptor)

    HttpHeaders httpHeaders = new HttpHeaders()
    headers.each {
      httpHeaders.add(it.key, it.value)
    }
    HttpEntity<?> requestEntity = new HttpEntity<>("body", httpHeaders)
    def status = restTemplate.exchange(uri, HttpMethod.resolve(method), requestEntity, String).getStatusCodeValue()
    callback?.call()
    return status
  }
}

[trask]

Maybe we could also test it the same way as we do for other http clients.

👍

[mateuszrzeszutek]

Maybe we could also test it the same way as we do for other http clients.

Yeah, definitely 🤦‍♂️ I don't know how I did not think of this earlier 😅

[mateuszrzeszutek]

Done!
I've left only one unit test with mocks: the one that verifies that we do not create a seconds CLIENT span. This test should also be added to the HttpClientTest, but let's do it in another PR.