Add fetch method configuration for UpdateSource

[cccs-rs]

"Probably wouldn't be too unreasonable to add a method field to UpdateSource:
https://cybercentrecanada.github.io/assemblyline4_docs/odm/models/service/#updatesource

And it could be an enum that supports GET, POST, SSH so it'll be more explicit when the updater tries to perform fetching (rather than trial and error that it's doing now)."

Additional context
Ref: https://discord.com/channels/908084610158714900/909870171643056150/1275266906622001172

[gdesmar]

It will be great to know if it is a GET or a GIT source for sure. 🙂

[eljeffeg]

I have one source that requires a POST, so looking forward to this when it gets added.

[eljeffeg]

Any ETA on this enhancement? 🙂

[cccs-rs]

I'll probably have time to implement this (and probably other features) during the winter break when we have a feature freeze and stage it for a new stable release in 2025 🤞🤞