docs: improve troubleshooting and handle integrity check failures

Previously, the utility aborted immediately when an integrity check
failed after restoring the database. It now prints a complete report
along with the specific error that triggered the failure, making it
easier to diagnose issues before exiting.

Author: sravotto

README.md

@@ -78,6 +78,67 @@ blobcheck s3 --uri 's3://mybucket/cluster1_backup?AWS_ACCESS_KEY_ID=..&AWS_SECRE
 └──────┴────────────┴─────────────┴────────┘
 ```
 
+## Troubleshooting
+
+When issues arise, you can use verbosity flags to understand what’s happening under the hood.
+
+### Enable Debug Output
+
+Running with `-v` enables debug logging. This shows all parameter combinations that `blobcheck` tries when connecting to the storage provider.
+
+For example, connecting to a MinIO server with default settings may fail if virtual host–style requests are used (where the bucket name is treated as part of the hostname):
+
+```text
+2025/09/29 14:32:54 DEBUG Trying params env="map[AWS_ACCESS_KEY_ID:cockroach AWS_ENDPOINT:http://localhost:29000 AWS_REGION:aws-global AWS_SECRET_ACCESS_KEY:******]"
+2025/09/29 14:32:54 DEBUG Failed to list objects error="operation error S3: ListObjectsV2, https response error StatusCode: 0, RequestID: , HostID: , request send failed, Get \"http://test.localhost:29000/?list-type=2\": dial tcp: lookup test.localhost: no such host" env="map
+```
+
+In this case, blobcheck will continue trying alternative combinations until it finds one that works. The first successful combination is then used for backup/restore validation.
+
+### Enable AWS SDK Tracing
+
+Adding a second -v flag provides even deeper insight by enabling AWS SDK trace logs. These include full request/response details exchanged with the storage provider.
+
+Using the same failing MinIO example, the output now shows the full request signature, headers, and why the request failed:
+
+
+```text
+2025/09/29 14:33:51 DEBUG Trying params env="map[AWS_ACCESS_KEY_ID:cockroach AWS_ENDPOINT:http://localhost:29000 AWS_REGION:aws-global AWS_SECRET_ACCESS_KEY:******]"
+SDK 2025/09/29 14:33:51 DEBUG Request Signature:
+---[ CANONICAL STRING  ]-----------------------------
+GET
+/
+list-type=2
+accept-encoding:identity
+amz-sdk-invocation-id:4fad79e8-9ae8-43ba-b2a1-7036342f9295
+amz-sdk-request:attempt=1; max=1
+host:test.localhost:29000
+x-amz-content-sha256:e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
+x-amz-date:20250929T183351Z
+
+accept-encoding;amz-sdk-invocation-id;amz-sdk-request;host;x-amz-content-sha256;x-amz-date
+e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
+---[ STRING TO SIGN ]--------------------------------
+AWS4-HMAC-SHA256
+20250929T183351Z
+20250929/us-east-1/s3/aws4_request
+7bbccaeea2b0816cf48e8b7e3e916fcb6d641044f7d9fd743c42eca6bcfc018b
+-----------------------------------------------------
+SDK 2025/09/29 14:33:51 DEBUG Request
+GET /?list-type=2 HTTP/1.1
+Host: test.localhost:29000
+User-Agent: aws-sdk-go-v2/1.39.0 ua/2.1 os/macos lang/go#1.24.2 md/GOOS#darwin md/GOARCH#arm64 api/s3#1.88.1 m/g
+Accept-Encoding: identity
+Amz-Sdk-Invocation-Id: 4fad79e8-9ae8-43ba-b2a1-7036342f9295
+Amz-Sdk-Request: attempt=1; max=1
+Authorization: AWS4-HMAC-SHA256 Credential=cockroach/20250929/us-east-1/s3/aws4_request, SignedHeaders=accept-encoding;amz-sdk-invocation-id;amz-sdk-request;host;x-amz-content-sha256;x-amz-date, Signature=e6ed31368624571de7b3b0bb01d658ada05001bb33a20217478c5f09aaaeee55
+X-Amz-Content-Sha256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
+X-Amz-Date: 20250929T183351Z
+
+SDK 2025/09/29 14:33:51 DEBUG request failed with unretryable error https response error StatusCode: 0, RequestID: , HostID: , request send failed, Get "http://test.localhost:29000/?list-type=2": dial tcp: lookup test.localhost: no such host
+2025/09/29 14:33:51 DEBUG Failed to list objects error="operation error S3: ListObjectsV2, https response error StatusCode: 0, RequestID: , HostID: , request send failed, Get \"http://test.localhost:29000/?list-type=2\": dial tcp: lookup test.localhost: no such host" env="map[AWS_ACCESS_KEY_ID:cockroach AWS_ENDPOINT:http://localhost:29000 AWS_REGION:aws-global AWS_SECRET_ACCESS_KEY:******]"
+```
+
 ---
 
 ## High-Level Architecture

internal/validate/validate.go

@@ -170,7 +170,9 @@ func (v *Validator) Validate(ctx *stopper.Context) (*Report, error) {
 	}
 
 	if err := v.verifyIntegrity(ctx, conn); err != nil {
-		return nil, err
+		// If we fail to verify the integrity, just log the error, but
+		// still provide a complete report
+		slog.Error("failed to verify integrity", slog.Any("error", err))
 	}
 
 	return &Report{