Feat/htsget seekable

[MalinAhlberg]

Related issue(s) and PR(s)
This PR closes #696 and neicnordic/sda-download#372.
It includes the changes of #820, but is based on #826 instead of #703.

Description

• Remove the second header for re-encryption (server-public-key)
• Remove the user-agent check for the requester
• The content-length is now including the header size when htsget requests the encrypted file size
• The range header returns an extra character, according to specification
• Includes the PR Seekable S3 support, second take #826 code, to make random access possible

How to test

• make sure full and partial files can be downloaded from the s3 endpoint
• make sure full and partial files can be downloaded from the s3-encrypted endpoint
• make sure it works with htsget (instructions: https://github.com/GenomicDataInfrastructure/starter-kit-htsget?tab=readme-ov-file#accessing-data-with-htsget)

Also see #701 and #776.

[aaperis]

We should merge this PR which also covers #820