Use a separate ENV variable for Authentication URL is supplied

[jason-fox]

Related #392 - This PR offers an alternative AUTHENTICATION_URL which means it can be different to the ACCESS_TOKEN_URL

The fallback is to use FIWARE_IDM_SERVER as previously

[coveralls]

Coverage decreased (-0.005%) to 78.94% when pulling 4867790 on jason-fox:feature/idm-url into 8418eac on Wirecloud:develop.

[aarranz]

Hi @jason-fox,

Thank you very much for your contributions. I'm missing some minor update on the installation guide regarding this new setting (on the IdM section) as well as some basic test to cover new code lines.

Regarding your current changes, everything looks great except the name of the setting. I prefer something like FIWARE_IDM_PUBLIC_URL. What do you think? Also, it would be great if @mjimenezganan can provide his opinion about the setting name.

[aarranz]

Hi @jason-fox, can you proceed an update the environment name?. Miguel is a bit busy to write here, but I've talked with him and he agrees.

[jason-fox]

@aarranz - PR has been fixed according to review.

• parameter has been renamed - 89cbdd2 & Wirecloud/docker-wirecloud@0002c51
• test added - 4867790

[aarranz]

Merging, Thank you very much for the contribution!