user camera FOV control in SDF files

[AzulRadio]

New feature

Part of gazebosim/gz-sim#421

Summary

Users can now change the FOV of the user camera in SDF as follows:

Test it

<sdf version="1.6">
    ...
    <gui fullscreen="0">

      <!-- 3D scene -->
      <plugin filename="MinimalScene" name="3D View">
        ...
        <fov>60</fov>
      </plugin>
      ...
    </gui>

Please enter the FOV in degree and by default ignition uses a FOV of 90

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (ign-gui6@c51789f). Click here to learn what that means.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             ign-gui6     #400   +/-   ##
===========================================
  Coverage            ?   30.54%           
===========================================
  Files               ?       41           
  Lines               ?     1748           
  Branches            ?        0           
===========================================
  Hits                ?      534           
  Misses              ?     1214           
  Partials            ?        0           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c51789f...752d120. Read the comment docs.

[jennuine]

Looks good, need some minor changes.

• Add the new element to the documentation here:

  gz-gui/src/plugins/minimal_scene/MinimalScene.hh

  Lines 46 to 63 in c1e7927

  	/// ## Configuration
  	///
  	/// * \<engine\> : Optional render engine name, defaults to 'ogre'. If another
  	/// engine is already loaded, that will be used, because only
  	/// one engine is supported at a time currently.
  	/// * \<scene\> : Optional scene name, defaults to 'scene'. The plugin will
  	/// create a scene with this name if there isn't one yet. If
  	/// there is already one, a new camera is added to it.
  	/// * \<ambient_light\> : Optional color for ambient light, defaults to
  	/// (0.3, 0.3, 0.3, 1.0)
  	/// * \<background_color\> : Optional background color, defaults to
  	/// (0.3, 0.3, 0.3, 1.0)
  	/// * \<camera_pose\> : Optional starting pose for the camera, defaults to
  	/// (0, 0, 5, 0, 0, 0)
  	/// * \<camera_clip\> : Optional near/far clipping distance for camera
  	/// * \<near\> : Camera's near clipping plane distance, defaults to 0.01
  	/// * \<far\> : Camera's far clipping plane distance, defaults to 1000.0
  	/// * \<sky\> : If present, sky is enabled.

In the PR description:

• Change Closes to Part of as there are other parameters we want to add (Github will close the PR if Closes is present)
• Update the 'Test it' portion to the correct sdf snippet as we discussed in the VC

[jennuine]

Nice work, thanks for iterating! One minor fix left and please fix the last 2 commits to include your sign-off so DCO will pass

[jennuine]

Please fix the code check error: https://github.com/gazebosim/gz-gui/runs/6493033767?check_suite_focus=true#step:4:4561