fix(azure_blob): make AccountName optional when BlobEndpoint is provided

[yoelk]

Summary

This PR fixes a regression introduced in v0.52.0 where AccountName became required in Azure Blob Storage connection strings, even when BlobEndpoint was provided. This broke existing configurations that relied on SAS tokens with blob endpoints.

The fix:

• When BlobEndpoint is provided but AccountName is missing, the account name is now automatically extracted from the endpoint URL
• Example: https://mystorageaccount.blob.core.windows.net/ → account name is mystorageaccount
• This restores v0.45.0 behavior and matches the intent described in the existing code comments

Changes made:

• Modified build_client() in src/sinks/azure_common/config.rs to make AccountName optional when BlobEndpoint is present
• Added extract_account_name_from_endpoint() helper function to parse account names from blob endpoint URLs
• Added comprehensive unit tests covering all connection string scenarios

Vector configuration

Connection string that was broken (now works):

[sinks.azure_blob]
type = "azure_blob"
connection_string = "BlobEndpoint=https://mystorageaccount.blob.core.windows.net/;SharedAccessSignature=sv=2021-01-01&sig=..."
container_name = "logs"

Connection string that still works (unchanged):

[sinks.azure_blob]
type = "azure_blob"
connection_string = "DefaultEndpointsProtocol=https;AccountName=myaccount;AccountKey=...;EndpointSuffix=core.windows.net"
container_name = "logs"

How did you test this PR?

Added unit tests in src/sinks/azure_common/config.rs:

• test_extract_account_name_from_endpoint - Tests URL parsing with various endpoint formats
• test_build_client_with_account_name_in_connection_string - Tests traditional connection strings with explicit AccountName
• test_build_client_with_blob_endpoint_and_account_name - Tests when both AccountName and BlobEndpoint are provided
• test_build_client_with_blob_endpoint_without_account_name - Tests the regression fix - BlobEndpoint without AccountName
• test_build_client_without_account_name_or_blob_endpoint - Tests proper error handling

Verified compilation with cargo check -p vector --lib

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

• Fixes: ENG-166496

Notes

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[mortenmj]

@vectordotdev/vector could we get this PR merged? We've been unable to keep up with recent versions due to this issue.

[mortenmj]

@thomasqueirozb are you able to help here?