Rename valid_domain to available_domain

valid_domain didn't really make as much sense, since that would be
more about the formatting of the domain, but it actually checks
formatting and also makes sure that there aren't any records existing
for it (that it is available to be registered for a new vhost)

Author: jvperrin

ocfweb/account/vhost.py

@@ -23,7 +23,7 @@
 from ocfweb.component.session import logged_in_user
 
 
-def valid_domain(domain):
+def available_domain(domain):
     if not re.match(r'^[a-zA-Z0-9]+\.berkeley\.edu$', domain):
         return False
     return not host_exists(domain)
@@ -283,7 +283,7 @@ def clean_requested_subdomain(self):
                 'Maybe add ".berkeley.edu" to the end?',
             )
 
-        if not valid_domain(requested_subdomain):
+        if not available_domain(requested_subdomain):
             raise forms.ValidationError(
                 'The domain you requested is not available. '
                 'Please select a different one.',

tests/account/vhost_test.py

@@ -1,12 +1,12 @@
 import pytest
 
-from ocfweb.account.vhost import valid_domain
+from ocfweb.account.vhost import available_domain
 from ocfweb.account.vhost import valid_domain_external
 
 
 @pytest.mark.parametrize(
     'domain,expected', [
-        # nxdomain
+        # nxdomain (should be available)
         ('asdfghjkl.berkeley.edu', True),
         ('kljasdlgjlsafdfhsadf.berkeley.edu', True),
 
@@ -37,8 +37,8 @@
         ('vns;alf iashf poasf bawen svn;', False),
     ],
 )
-def test_valid_domain(domain, expected):
-    assert valid_domain(domain) is expected
+def test_available_domain(domain, expected):
+    assert available_domain(domain) is expected
 
 
 @pytest.mark.parametrize(