Please add support for displaying per-app "access denied" contact instructions.

[floatingatoll]

When denied access to an application due to non-membership in the required groups, the SSO application currently emits the same error text for all applications:

elif error_code == "notingroup":
    error_text = "Sorry, you do not have permission to access {client}.  \
    Please contact eus@mozilla.com if you should have access.".format(
        client=self.data.get("client")
)

sso-dashboard/dashboard/auth.py

Line 148 in dbc38cc

error_text = "Sorry, you do not have permission to access {client}. \

Please allow individual SSO applications to override eus@mozilla.com and replace it with their own text, when they choose to activate that override in apps.yml. This will vastly reduce the number of false positive support requests directed incorrectly to EUS and permit application owners to accurately exercise control over access to their applications.