Minimum Working Example for a model that loads both gz-sim and gazebo classic plugins

test_model.world

<?xml version="1.0"?>
<sdf version="1.7">
    <world name="example_world">
        <model name="camera_model">
            <static>true</static>
            <pose>0 0 0.1 0 0 0</pose>
            <link name="link">
                <visual name="visual">
                    <geometry>
                        <box>
                            <size>0.1 0.1 0.1</size>
                        </box>
                    </geometry>
                </visual>
                <sensor name="camera_sensor" type="camera">
                    <camera>
                        <horizontal_fov>1.5708</horizontal_fov>
                        <image>
                            <width>640</width>
                            <height>480</height>
                        </image>
                        <clip>
                            <near>0.1</near>
                            <far>100</far>
                        </clip>
                    </camera>
                    <always_on>1</always_on>
                    <update_rate>30</update_rate>
                    <visualize>true</visualize>
                    <!-- Gazebo Classic plugin -->
                    <plugin name="camera_plugin" filename="libCameraPlugin.so">
                    </plugin>

                    <!-- gz-sim plugin -->
                    <plugin filename="gz-sim-camera-video-recorder-system"  name="gz::sim::systems::CameraVideoRecorder">
                        <service>camera/record_video</service>
                    </plugin>
                </sensor>
            </link>
        </model>
    </world>
</sdf>