Blob Service: Signature File Generation, Missing REST Endpoint for Download

[MGTheTrain]

Describe the bug
The signing process in the Blob Service is not functioning correctly. The generated signature content is not being uploaded as expected. Additionally, there is no REST endpoint available to download the signature file once it's uploaded.

To Reproduce
Steps to reproduce the behavior:

1. Generate an RSA or EC key pair
2. Initiate the file signing process in the Blob Service on POST '/api/v1/cvs/blobs' by selecting a file to upload and the signing key id (the private key of the generated key pair)
3. No endpoint available for downloading the signature file or verifying integrity of the signed file trough the system

Expected behavior

The expected behavior is for the generated signature file iscorrectly uploaded to the Blob Service. Additionally, a REST endpoint should be available to allow users to download the signature file when needed.

Screenshots
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Hardware specs (please complete the following information):

OS: Linux Debian
Version: 12
Additional context
The issue needs to be addressed by fixing the signature generation and upload process and implementing a REST endpoint for downloading signature files. This update will ensure smoother operation for users handling signed files in the Blob Service.