Set-up conda package hosting for phoenix2 library

We need to find a solution to host the phoenix2 conda channel. Possible solutions:

• host on conda-forge
  • pros: available for free, supported by very big community
  • cons:
    • suited to host release packages, not development packages that should be eventually removed: conda-forge prevents to remove uploaded packages
    • need to request feedstock maintainers to add packages (usually accepted in few days)
    • less control on building infrastructure
    • on github
• host a server on LAPP infra using quetz
  • pros: full control on the server, channels, packages, infra
  • cons: maintenance cost
• host at prefix.dev channels
  • pros:
    • no maintenance cost for the channel hosting
    • can control package creation and infra (use CI/CD)
    • can delete/add packages with API, use several channels, etc. -> suited for development and release
  • cons:
    • hosted by private company (paid by sponsors of big player in the community, but still)

The best solution at the moment appears to be using prefix.dev channels.

Task list:

• #5 (closed) - Get a shared account mail to open a "phoenix" account owning phoenix and phoenix-dev the channels, open individual accounts for maintainers.
• #7 (closed) - Get API key and store it in gitlab masked variable. Ideal solution would be to use external secret provider, see gitlab variables security, but that requires higher gitlab subsription tier

FYI @thibaut.oprinsen @paubert