Basic labels support

Adds basic labels support to the registry code (V2), and the API. Note that this does not yet add any UI related support.

test/test_validation.py

@@ -0,0 +1,44 @@
+import unittest
+from util.validation import validate_label_key
+
+class TestLabelKeyValidation(unittest.TestCase):
+  def assertValidKey(self, key):
+    self.assertTrue(validate_label_key(key))
+
+  def assertInvalidKey(self, key):
+    self.assertFalse(validate_label_key(key))
+
+  def test_basic_keys(self):
+    self.assertValidKey('foo')
+    self.assertValidKey('bar')
+
+    self.assertValidKey('foo1')
+    self.assertValidKey('bar2')
+
+    self.assertValidKey('1')
+    self.assertValidKey('12')
+    self.assertValidKey('123')
+    self.assertValidKey('1234')
+
+    self.assertValidKey('git-sha')
+
+    self.assertValidKey('com.coreos.something')
+    self.assertValidKey('io.quay.git-sha')
+
+  def test_invalid_keys(self):
+    self.assertInvalidKey('')
+    self.assertInvalidKey('git_sha')
+
+  def test_must_start_with_alphanumeric(self):
+    self.assertInvalidKey('-125')
+    self.assertInvalidKey('-foo')
+    self.assertInvalidKey('foo-')
+    self.assertInvalidKey('123-')
+
+  def test_no_double_dashesdots(self):
+    self.assertInvalidKey('foo--bar')
+    self.assertInvalidKey('foo..bar')
+
+
+if __name__ == '__main__':
+  unittest.main()