Artifactory should use a token instead of the "xray" user for communicating with Xray

Currently, Artifactory communicates with Xray via a special user called "xray" created in the initial handshake between the products. This is a tech debt and far from the ideal way for the two products to communicate.
Since we moved to use Access tokens, Xray should provide Artifactory with a token, and Artifactory should persist it and use it whenever needed.