Expose access token under developer tools

I need this from time to time. For example, debugging an API call or
scripting something with the admin API. This is buried under developer
settings so hopefully no one starts sharing this willy-nilly.

Element Web does something similar, except theirs is hidden under Help &
About.

src/devtools/AccountData.qml

@@ -33,4 +33,28 @@ ColumnLayout {
             }
         }
     }
+    FormCard.FormCard {
+        FormCard.FormSwitchDelegate {
+            id: showAccessTokenCheckbox
+            text: i18nc("@info", "Show Access Token")
+            description: i18n("This should not be shared with anyone, even other users. This token gives full access to your account.")
+        }
+        FormCard.FormTextDelegate {
+            text: i18nc("@info", "Access Token")
+            description: root.connection.accessToken
+            visible: showAccessTokenCheckbox.checked
+
+            contentItem.children: QQC2.Button {
+                text: i18nc("@action:button", "Copy access token to clipboard")
+                icon.name: "edit-copy"
+                display: QQC2.AbstractButton.IconOnly
+
+                onClicked: Clipboard.saveText(root.connection.accessToken)
+
+                QQC2.ToolTip.text: text
+                QQC2.ToolTip.delay: Kirigami.Units.toolTipDelay
+                QQC2.ToolTip.visible: hovered
+            }
+        }
+    }
 }