Multiple errors across the UI appear as json strings

[Steve Rydz]

When enabling DHCP or relaying VLAN, if there is an error, for example enabling DHCP without specifying a primary rack or relaying VLAN to an invalid VLAN the error comes back as a JSON string.

Screenshot: https://images.zenhubusercontent.com/5a9d4ee34b5806bc2bc9694d/14579fd7-4019-465f-b1ae-e9c5984aebf6

It's not possible to simply parse this client side as the key isn't always the same. I have seen it as `__relay__` rather than `__all__`, and other times it's been just a string.

Ideally a string will always be returned, otherwise if a JSON response is necessary it should be consistent so it can be parsed client side.

[Andres Rodriguez (andreserl)]

This is an error across all of the UI. This is because the API returns a json string but the error handling on the UI doesn't deal with that correctly.

[Steve Rydz (steverydz)]

The errors come back to the UI as either a string or a JSON string so it's unpredictable, and in the case that it is a JSON string the format is inconsistent e.g. `__relay__` as a key in one case, `__all__` in another as examples.

[Thorsten Merten (thorsten-merten)]

Might be a frontend, an inconsistency how errors communicated or a mix of both