Space characters in ReturnTo query parameter cause redirect failure

Problem/Motivation

It seems that having a space character in the ReturnTo query parameter causes certain things to break down.

Steps to reproduce

Attempting to sign into a site via https://example.com/saml_login?ReturnTo=https://example.com/some%20path will lead to the user not being returned to /some%20path, but rather the default user profile page.

Proposed resolution

N/A

Remaining tasks

User interface changes

API changes

Data model changes