Improve network handling

[thomas-senechal]

Context
For now, we can only switch between 3 networks. Those networks are listed in config_network.yaml and embedded in the Station binary.
The front end displays the list of networks available in the yaml file, but the endpoint to change network (POST /network/{network}) only accepts testnet, buildnet and labnet, so if we add a network to the yaml file, it's not possible to change the used network to this network.

A solution to this issue is to remove the enum of the POST /network/{network} endpoint so we can use any network from the yaml file.

User flow
Describe the user flow using user stories so the end result is super clear - PM

How to

• Remove the enum for POST /network/{network}
• Ensure that the asked network is in the config_network.yaml

Technical details
Give the technical insights so anyone in the team can tackle the tasks - Dev

QA testing
Does this task require some QA tests ?
If yes, explain how to validate it

[thomas-senechal]

Need to be discussed

We could also add the possibility for the users to create config file in the config directory that would add some available networks. That would allow them to add a local (or distant) node and allow us to use custom nodes or DNS for development.

[B-Naoufal]

yes, We can an endpoint just for that!

[Thykof]

related to #1317