Use card view for DSN

app/src/main/res/layout/activity_dsn.xml

@@ -9,6 +9,9 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:orientation="vertical"
+        android:paddingHorizontal="6dp"
+        android:paddingVertical="12dp"
+        android:scrollbarStyle="outsideOverlay"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toTopOf="parent">
 
@@ -16,25 +19,45 @@
             android:layout_width="match_parent"
             android:layout_height="wrap_content">
 
-            <eu.faircode.email.FixedTextView
-                android:id="@+id/tvHeaders"
-                android:layout_width="0dp"
+            <androidx.cardview.widget.CardView
+                android:id="@+id/cardMessage"
+                android:layout_width="match_parent"
                 android:layout_height="wrap_content"
-                android:layout_marginTop="3dp"
-                android:fontFamily="monospace"
-                android:minHeight="60dp"
-                android:text="Headers"
-                android:textAppearance="@style/TextAppearance.AppCompat.Small"
-                android:textIsSelectable="true"
+                android:layout_marginHorizontal="3dp"
+                app:cardBackgroundColor="?attr/colorCardBackground"
+                app:cardCornerRadius="6dp"
+                app:cardElevation="0dp"
                 app:layout_constraintEnd_toEndOf="parent"
                 app:layout_constraintStart_toStartOf="parent"
-                app:layout_constraintTop_toTopOf="parent" />
+                app:layout_constraintTop_toTopOf="parent">
 
-            <androidx.constraintlayout.widget.Group
-                android:id="@+id/grpReady"
-                android:layout_width="0dp"
-                android:layout_height="0dp"
-                app:constraint_referenced_ids="tvHeaders" />
+                <androidx.constraintlayout.widget.ConstraintLayout
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:paddingHorizontal="6dp"
+                    android:paddingVertical="12dp">
+
+                    <eu.faircode.email.FixedTextView
+                        android:id="@+id/tvHeaders"
+                        android:layout_width="0dp"
+                        android:layout_height="wrap_content"
+                        android:layout_marginTop="3dp"
+                        android:fontFamily="monospace"
+                        android:minHeight="60dp"
+                        android:text="Headers"
+                        android:textAppearance="@style/TextAppearance.AppCompat.Small"
+                        android:textIsSelectable="true"
+                        app:layout_constraintEnd_toEndOf="parent"
+                        app:layout_constraintStart_toStartOf="parent"
+                        app:layout_constraintTop_toTopOf="parent" />
+
+                    <androidx.constraintlayout.widget.Group
+                        android:id="@+id/grpReady"
+                        android:layout_width="0dp"
+                        android:layout_height="0dp"
+                        app:constraint_referenced_ids="tvHeaders" />
+                </androidx.constraintlayout.widget.ConstraintLayout>
+            </androidx.cardview.widget.CardView>
         </androidx.constraintlayout.widget.ConstraintLayout>
     </eu.faircode.email.ScrollViewEx>