feature: advanced file conversion

[Integer-Ctrl]

Feature Request

Describe the feature you'd like
The on-the-fly conversion during download works, but could be improved for greater convenience:

• Decompress files on download (from detected compression to file w/o compression)
• Compress files without compression on download (from file w/o compression to specified compression)
• Refactor file conversion logic to databusclient/extensions/file_converter.py
• Currently the conversion feels slow. I didn't test whether this is reasonable or if this could be improved. An idea would be to add the conversion (and also checksum computation/validation) directly to the download step. Now the files is first downloaded completely and then converted. Maybe this can be squashed into one step.

Why is this feature important?
Explain the benefit or use case. Is your feature request related to a problem?
Follow up on #18. Not urgent, but useful for greater functionality

Describe alternatives you've considered
For now: manually

[Dev10-sys]

This makes sense. Integrating conversion and checksum validation into the download step could improve performance.
I’m currently focusing on small cleanups, but happy to help later once the approach is clarified.

[Tahoora-Tabassum]

One idea I had is to treat the download, (de)compression, and checksum as a small streaming pipeline rather than separate steps — so the download stream passes through optional processors (decompressor, compressor, checksum) before being written to disk.

I could start with a minimal version (gzip + checksum only) to address this issue, and later this could be extended to support more formats or features if that fits the project’s direction. Would this approach make sense here?