feat: add PROJECT_CREATE_ALLOW_ALL environment variable

[NathanVss]

Based on this discussion: #520

The goal is to provide a simple way to allow any user to create a project, where only admin can do it at the moment.

Server

Add this environment variable to server/.env

PROJECT_CREATE_ALLOW_ALL=true

Client

Add this environment variable to client/.env

REACT_APP_PROJECT_CREATE_ALLOW_ALL=true

Thoughts

I used the easiest approach in order to allow us to start using Planka the quickest as possible. But I am not 100% fan of having to duplicate the configuration on the client and the server, imo the best way to do it, is to only keep the server environment variable and make the client load a configuration from an api route /config on first load, where the server would expose configuration parameters like this:

HTTP CODE 200 

{
    "projectCreateAllowAll": true
}

But it would imply more fondamental changes and I don't sufficiently know the client architecture yet to estimate how much, and I think this PR is at least a good starting point to discuss about it.

🙏

[CLAassistant]

All committers have signed the CLA.

[meltyshev]

Thanks! I fixed it a bit to only require specifying this env variable on the server, and changed the name of the environment variable.