Do not use etag or if-modified-since for gitlab artifacts urls

Signed-off-by: Fabio Valente <8777512+fabiojvalente@users.noreply.github.com>

.changeset/plenty-bobcats-drum.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-defaults': minor
+---
+
+Do not send etag or If-Modified-Since headers for gitlab artifact urls

packages/backend-defaults/src/entrypoints/urlReader/lib/GitlabUrlReader.ts

@@ -74,6 +74,7 @@ export class GitlabUrlReader implements UrlReaderService {
     options?: UrlReaderServiceReadUrlOptions,
   ): Promise<UrlReaderServiceReadUrlResponse> {
     const { etag, lastModifiedAfter, signal, token } = options ?? {};
+    const isArtifact = url.includes('/-/jobs/artifacts/');
     const builtUrl = await this.getGitlabFetchUrl(url);
 
     let response: Response;
@@ -81,10 +82,11 @@ export class GitlabUrlReader implements UrlReaderService {
       response = await fetch(builtUrl, {
         headers: {
           ...getGitLabRequestOptions(this.integration.config, token).headers,
-          ...(etag && { 'If-None-Match': etag }),
-          ...(lastModifiedAfter && {
-            'If-Modified-Since': lastModifiedAfter.toUTCString(),
-          }),
+          ...(etag && !isArtifact && { 'If-None-Match': etag }),
+          ...(lastModifiedAfter &&
+            !isArtifact && {
+              'If-Modified-Since': lastModifiedAfter.toUTCString(),
+            }),
         },
         // TODO(freben): The signal cast is there because pre-3.x versions of
         // node-fetch have a very slightly deviating AbortSignal type signature.