Add OIDC fixes, add prefered_username, add application-user claims

app/services/concerns/claims_merger.rb

@@ -0,0 +1,35 @@
+module ClaimsMerger
+  extend ActiveSupport::Concern
+
+  # Deep merge claims, combining arrays instead of overwriting them
+  # This ensures that array values (like roles) are combined across group/user/app claims
+  #
+  # Example:
+  #   base = { "roles" => ["user"], "level" => 1 }
+  #   incoming = { "roles" => ["admin"], "department" => "IT" }
+  #   deep_merge_claims(base, incoming)
+  #   # => { "roles" => ["user", "admin"], "level" => 1, "department" => "IT" }
+  def deep_merge_claims(base, incoming)
+    result = base.dup
+
+    incoming.each do |key, value|
+      if result.key?(key)
+        # If both values are arrays, combine them (union to avoid duplicates)
+        if result[key].is_a?(Array) && value.is_a?(Array)
+          result[key] = (result[key] + value).uniq
+        # If both values are hashes, recursively merge them
+        elsif result[key].is_a?(Hash) && value.is_a?(Hash)
+          result[key] = deep_merge_claims(result[key], value)
+        else
+          # Otherwise, incoming value wins (override)
+          result[key] = value
+        end
+      else
+        # New key, just add it
+        result[key] = value
+      end
+    end
+
+    result
+  end
+end