Allow blank S3 regions to be used

If consolidated object storage is used without a region, Workhorse will
fall back to making a direct HTTP PUT call to the S3 endpoint because
GitLab Rails does not send the multipart upload URLs in this mode.

However, this will result a 411 Length Required error because multipart
upload URLs must be used when the Content-Length header is not
available.

An S3 region is not strictly required, particularly with Minio. With
Amazon S3, the region will default to US East (`us-east-1`). If the
bucket does not exist in the region, S3 will return with a more
informative error.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/297227

changelogs/unreleased/sh-allow-blank-s3-region.yml

+---
+title: Allow blank S3 regions to be used
+merge_request: 677
+author:
+type: changed

internal/filestore/save_file_opts.go

@@ -146,7 +146,7 @@ func (c *ObjectStorageConfig) IsGoCloud() bool {
 
 func (c *ObjectStorageConfig) IsValid() bool {
 	if c.IsAWS() {
-		return c.S3Config.Bucket != "" && c.S3Config.Region != "" && c.s3CredentialsValid()
+		return c.S3Config.Bucket != "" && c.s3CredentialsValid()
 	} else if c.IsGoCloud() {
 		// We could parse and validate the URL, but GoCloud providers
 		// such as AzureRM don't have a fallback to normal HTTP, so we

internal/filestore/save_file_opts_test.go

@@ -187,6 +187,9 @@ func TestUseWorkhorseClientEnabled(t *testing.T) {
 	iamConfig := missingCfg
 	iamConfig.S3Config.UseIamProfile = true
 
+	missingRegion := cfg
+	missingRegion.S3Config.Region = ""
+
 	tests := []struct {
 		name                string
 		UseWorkhorseClient  bool
@@ -245,6 +248,13 @@ func TestUseWorkhorseClientEnabled(t *testing.T) {
 			},
 			expected: false,
 		},
+		{
+			name:                "missing S3 region",
+			UseWorkhorseClient:  true,
+			remoteTempObjectID:  "test-object",
+			objectStorageConfig: missingRegion,
+			expected:            true,
+		},
 	}
 
 	for _, test := range tests {