Add license upload step to the setup flow

Fixes #853

util/config/provider/baseprovider.py

@@ -75,8 +75,12 @@ class BaseProvider(object):
     """ Returns whether the file with the given name exists under the config override volume. """
     raise NotImplementedError
 
-  def get_volume_file(self, filename, mode='r'):
-    """ Returns a Python file referring to the given name under the config override volumne. """
+  def get_volume_file(self, filename):
+    """ Returns a Python file referring to the given name under the config override volume. """
+    raise NotImplementedError
+
+  def write_volume_file(self, filename, contents):
+    """ Writes the given contents to the config override volumne, with the given filename. """
     raise NotImplementedError
 
   def save_volume_file(self, filename, flask_file):
@@ -91,6 +95,14 @@ class BaseProvider(object):
     """
     raise NotImplementedError
 
+  def _get_license_file(self):
+    """ Returns the contents of the license file. """
+    try:
+     return self.get_volume_file(LICENSE_FILENAME)
+    except IOError:
+     msg = 'Could not open license file. Please make sure it is in your config volume.'
+     raise LicenseError(msg)
+
   def validate_license(self, config):
     """ Validates that the configuration matches the license file (if any). """
     if not config.get('SETUP_COMPLETE', False):
@@ -102,11 +114,10 @@ class BaseProvider(object):
     self.license = decode_license(license_file_contents)
     self.license.validate(config)
 
-  def _get_license_file(self):
-    """ Returns the contents of the license file. """
-    try:
-      return self.get_volume_file(LICENSE_FILENAME)
-    except IOError:
-      msg = 'Could not open license file. Please make sure it is in your config volume.'
-      raise LicenseError(msg)
+  def save_license(self, license_file_contents):
+    """ Saves the given contents as the license file. """
+    self.write_volume_file(LICENSE_FILENAME, license_file_contents)
 
+  def has_license_file(self):
+    """ Returns true if a license file was found in the config directory. """
+    return self.volume_file_exists(LICENSE_FILENAME)