Proposal: Add support for background locations in audit

[yanokwa]

In the XForms spec audit is placed in the meta block under the orx namespace. It uses a binary data type. See opendatakit/xforms-spec#94

<orx:meta>
	<orx:audit/>
</orx:meta>
<bind nodeset="/orx:meta/orx:audit" type="binary"/>

I propose we add the following bind attributes in the odk namespace to the specification. All three attributes are required to enable location audits and location-age must be greater than or equal to location-interval.

<bind nodeset="/orx:meta/orx:audit" type="binary" 
           odk:location-priority="balanced" odk:location-min-interval="10" odk:location-max-age="60" />

We have an implementation for Collect at getodk/collect#2772

[yanokwa]

@MartijnR @tiritea Any immediate reactions to this proposal?

[tiritea]

Other than putting on my tinfoil hat, nothing from me... ;-)

[MartijnR]

Looks great to me!

[yanokwa]

@MartijnR Do you ever see Enketo adding this feature? I ask because if it's possible, I want to make sure we've named things sensibly. @tiritea, same question.

[tiritea]

Unfortunately, I'm WAAAAY too late to the #94 party, so I'll have to defer to y'alls expertise that this <meta> stuff is the best place to persist such data :-) [personally, I'm not terribly fond of <meta>, but that's just me...].

In regards to actual naming, I'm easy; so long at all the required parameters are defined.

And as @MartijnR said, I've got far more pressing things to catch up on (repeat groups!) before I can even start to worry about background audits, sigh.

[MartijnR]

I am not seeing this (and other audit) feature getting into Enketo due to the difficulties in mimicking the same events in web clients, coupled with the lack of demand so far, but if that is resolved and changes, these attribute names make sense. They are prefixed with location- which is very sensible, and properly name-spaced. Not sure what location-priority does, but trust this makes sense and is logical. :)