Add option to pass URLs (dacat etc)

[minottic]

We will need to test the CLI with v3 and v4 in parallel, so having a way to pass vars could be handy. Something as easy as this, maybe, but I leave it up to you to decide how. It could also be a command line argument otherwise

func getEnv(key, fallback string) string {
    if value, ok := os.LookupEnv(key); ok {
        return value
    }
    return fallback
}

const MANUAL = "http://melanie.gitpages.psi.ch/SciCatPages"

var PROD_API_SERVER string = getEnv("PROD_API_SERVER", "https://dacat.psi.ch/api/v3")
var TEST_API_SERVER string = getEnv("TEST_API_SERVER", "https://dacat-qa.psi.ch/api/v3")
var DEV_API_SERVER string = getEnv("DEV_API_SERVER", "https://dacat-development.psi.ch/api/v3")
const LOCAL_API_SERVER string = "http://backend.localhost/api/v3"
var TUNNEL_API_SERVER string = getEnv("TUNNEL_API_SERVER", "https://dacat-development.psi.ch:5443/api/v3")

[sbliven]

I don't think we need more than one env variable. I would suggest

SCICATCLI_API_SERVER=https://scicat.development.psi.ch/api/v3
SCICATCLI_RSYNC_SERVER=pbt-archive.psi.ch
# or on the CLI
scicat-cli datasetIngestor --api-server=https://scicat.development.psi.ch/api/v3 --rsync-server=pbt-archive.psi.ch ...

Then the hard-coded constants are just used to set defaults.

The DEV_API_SERVER should be updated to https://scicat.development.psi.ch/api/v3. I think we should remove or deprecate the 'local' and 'tunnel' environments, since they can be covered in a more generic way now. The testenv and devenv options are convenient shortcuts, so let's keep them.