Handle case where the frontend url already contains query parameters

[PythonCoderAS]

To my knowledge, if there is a "?" in the URL, everything after is a query parameter, so we check for a "?" and if one does exist we use "&" instead of "?".

Fix #365

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[mostafa]

How about using urllib? https://stackoverflow.com/a/64117554/6999563

[PythonCoderAS]

How about using urllib? https://stackoverflow.com/a/64117554/6999563

Not necessarily because the frontend url might be a relative URL (ie "/login" and not "http://my-domain.com/login") which won't parse under urlparse

Coverage dropped. It would be nice to add a test.

[mostafa]

@PythonCoderAS It would be nice if you could add a test as well.