new: support autosend and autodelete

[florianm]

Add support to optionally override Collect's autosend and autodelete form management settings.

• Closes Support for auto-send and auto-delete #165
• Form properties (index.erb): add two dropdowns for each setting - empty on legacy forms, three options default, always, never.
• The dropdowns are styled like the other form properties elements (styles.css).
• The form data is plumbed through data.js to end up as a child node in the model, tacking onto what submission_url does.
• Screenshot 1: with options always and never, respectively
  
• Screenshot 2: with option "default" = "Follow ODK Collect settings"
  
• When loading a new form from "My forms", autosend and autodelete are loaded from that form.
• When exporting to XML with autosend always, autodelete never:
  • New namespace orx
  • New model child <submission method="form-data-post" orx:auto-send="true" orx:auto-delete="false"/>

<h:html xmlns="http://www.w3.org/2002/xforms" xmlns:h="http://www.w3.org/1999/xhtml" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:jr="http://openrosa.org/javarosa" xmlns:ev="http://www.w3.org/2001/xml-events" xmlns:orx="http://openrosa.org/xforms" xmlns:odk="http://www.opendatakit.org/xforms">
  <h:head>
    <h:title>Untitled Form</h:title>
    <model>
      <instance>
        <data id="Untitled-Form" version="1643332534">
          <meta>
            <instanceID/>
          </meta>
          <untitled2/>
        </data>
      </instance>
      <itext>
        <translation lang="English">
          <text id="/data/untitled2:label">
            <value>test</value>
          </text>
        </translation>
      </itext>
      <bind nodeset="/data/meta/instanceID" type="string" readonly="true()" jr:preload="uid"/>
      <submission method="form-data-post" orx:auto-send="true" orx:auto-delete="false"/>
      <bind nodeset="/data/untitled2" type="string"/>
    </model>
  </h:head>
  <h:body>
    <input ref="/data/untitled2">
      <label ref="jr:itext('/data/untitled2:label')"/>
    </input>
  </h:body>
</h:html>

• With both settings to "default" (follow Collect), no submission method node is inserted.
• With only one setting to non-default (e.g. autosend always, autodelete default), only the non-default is exported:

      <submission method="form-data-post" orx:auto-send="true"/>

• Export to XLSForm does not break, but also silently drops the autosend/autodelete settings.
• Once this PR is merged, I'll send a PR for metadata kinds email and audit to conclude the rework of Support audit, email, bearing #266.

[lognaturel]

Looks great!

Export to XLSForm does not break, but also silently drops the autosend/autodelete settings.

Is the idea to address this eventually, then?

[florianm]

Absolutely! Tracked at getodk/build2xlsform#22