[Feature Request] Time dimension without a backend db?

[ashleysommer]

I'm trying to get a WMS-T compliant time dimension working on the Mapcache WMS/WMTS server.
I'd prefer not to have to set up a ES, PG, or SQLite db alongside the mapcache.xml file in order to use a time dimension.
I'd like to specify a OCG-compatible ISO8601 Time period, like this:

<dimension type="values" name="time" default="2021-02-01" unit="ISO8601">
  <value>2015-11-20/2021-01-01/P1D</value>
</dimension>

Doing it this way, it does enable a time dimension, and include the correct XML in the GetCapabilities:

<Dimension name="time" default="2021-02-01" units="ISO8601">2015-11-20/2021-01-01/P1D</Dimension>

However passing any real time string for "time" dimension understandably results in "Failed to validate requested value for dimension", because it doesn't match the given value string.

I kind-of got around this, by setting it up as a regex:

<dimension type="regex" name="time" default="2021-02-01" unit="ISO8601">
  <regex>^[0-9]{4}-[0-9]{2}-[0-9]{2}[^&?]*$</regex>
</dimension>

That now works, and allows ISO Time strings to be passed in the query. However it breaks the GetCapabilities response:

<Dimension name="time" default="2021-02-01" units="ISO8601">^[0-9]{4}-[0-9]{2}-[0-9]{2}[^&?]*$</Dimension>

That confuses the WMS clients.

So this feature request is for a simple ISO8601 time dimension, specified by a time period string, that does not use a db to lookup the values.