Refactor and research moving CI/CD from Flux to ADO Pipelines possibilities

[niknii-vincit]

The current CI/CD pipeline setup with Flux has been unreliable as of late. It requires an increasing amount of work to maintain it, and it's complexity is rising.

Flux is a custom solution for this product, mainly done by someone who has left this project long ago and it has been left mostly as a black box, so we don't know with certainty wha and why it does what it does.

Additionally it's still dependent on the left person's credentials, which is a risk itself.

• Research 1. how to not be dependent on one person's credentials in CI/CD #1745
• Research 2. migrate Flux repository content to ADO (pipelines)
• Discuss & create new tickets for implementation: Teemu, Niki, Jarkko

Flux process can be found here https://dev.azure.com/hslfi/JORE%204.0/_wiki/wikis/JORE-4.0.wiki/3130/Continuous-Integration-Continuous-Delivery#

[ellinooraikaheimo]

Specify this ticket @culka @jarkkoka @niknii-vincit