Change test IdP settings

[brunato]

This PR updates settings of test IdPs, adding also a couple of configuration settings for SPID validator, useful when the onboarding procedure has to be done. Some settings ere renamed in order to match the current meaning of the configuration entry. When a test IdP is activated its name is added to the rendered spid_button.html template, so one doesn't need to provide an override to remove test IdPs from SPID button, but simply change the settings.

Changes:

• Add SPID_VALIDATOR_IDP_ACTIVE and SPID_VALIDATOR_METADATA_URL
• SPID_SAML_CHECK_DEMO_REMOTE_METADATA_ACTIVE -> SPID_DEMO_IDP_ACTIVE
• SPID_SAML_CHECK_DEMO_METADATA_URL -> SPID_DEMO_METADATA_URL
• SPID_SAML_CHECK_REMOTE_METADATA_ACTIVE -> SPID_SAML_CHECK_IDP_ACTIVE
  (also checking the old name as fallback)
• New template tags for checking if add test IdPs to SPID button

Note: it could be have a sense to add SPID validator and SPID Demo metadata to package or otherwise to update the update_idps.py script to download also their metadata.

[peppelinux]

great, thank you