Validate OAuth Redirect URIs (#32643)

This fixes a TODO in the code to validate the RedirectURIs when adding
or editing an OAuth application in user settings.

This also includes a refactor of the user settings tests to only create
the DB once per top-level test to avoid reloading fixtures.

modules/util/truncate.go

@@ -41,6 +41,8 @@ func SplitStringAtByteN(input string, n int) (left, right string) {
 
 // SplitTrimSpace splits the string at given separator and trims leading and trailing space
 func SplitTrimSpace(input, sep string) []string {
+	// Trim initial leading & trailing space
+	input = strings.TrimSpace(input)
 	// replace CRLF with LF
 	input = strings.ReplaceAll(input, "\r\n", "\n")