settings: Set a default for SSO_APPEND_DOMAIN.
settings: Set a default for SSO_APPEND_DOMAIN.

This means that if a user comments out the field in
/etc/zulip/settings.py, they won't get an error.

eeshangarg/zulip,rht/zulip,showell/zulip,hackerkid/zulip,andersk/zulip,tommyip/zulip,tommyip/zulip,brainwane/zulip,rishig/zulip,shubhamdhama/zulip,eeshangarg/zulip,shubhamdhama/zulip,timabbott/zulip,zulip/zulip,rishig/zulip,punchagan/zulip,kou/zulip,tommyip/zulip,zulip/zulip,brainwane/zulip,punchagan/zulip,hackerkid/zulip,rishig/zulip,synicalsyntax/zulip,zulip/zulip,hackerkid/zulip,kou/zulip,kou/zulip,showell/zulip,punchagan/zulip,timabbott/zulip,synicalsyntax/zulip,eeshangarg/zulip,hackerkid/zulip,zulip/zulip,eeshangarg/zulip,punchagan/zulip,rht/zulip,timabbott/zulip,timabbott/zulip,shubhamdhama/zulip,brainwane/zulip,andersk/zulip,showell/zulip,rht/zulip,kou/zulip,punchagan/zulip,tommyip/zulip,andersk/zulip,punchagan/zulip,tommyip/zulip,showell/zulip,brainwane/zulip,synicalsyntax/zulip,hackerkid/zulip,tommyip/zulip,eeshangarg/zulip,tommyip/zulip,zulip/zulip,rht/zulip,hackerkid/zulip,showell/zulip,punchagan/zulip,rht/zulip,kou/zulip,synicalsyntax/zulip,brainwane/zulip,zulip/zulip,zulip/zulip,shubhamdhama/zulip,shubhamdhama/zulip,eeshangarg/zulip,rishig/zulip,shubhamdhama/zulip,andersk/zulip,rht/zulip,hackerkid/zulip,andersk/zulip,eeshangarg/zulip,timabbott/zulip,synicalsyntax/zulip,brainwane/zulip,shubhamdhama/zulip,synicalsyntax/zulip,showell/zulip,andersk/zulip,rishig/zulip,timabbott/zulip,rishig/zulip,rishig/zulip,showell/zulip,brainwane/zulip,kou/zulip,timabbott/zulip,rht/zulip,synicalsyntax/zulip,kou/zulip,andersk/zulip