Updated redirect URI setup
Based on the feedback from Synology's developers, and testing: the redirect URI should not contain #/signup as it breaks authentication if multiple redirect URIs have to be set.
Based on DSM 7.2's code itself, Host and HTTPS headers are used internally to match the corresponding entry in the list.
Hope that can help, this is from days of testing + discussing with the support and dev teams.
Signed-off-by: Florent <Wr0ngName@users.noreply.github.com>