OWS Release 1.8.23

In addition to the standard animated handlers previously supported by all style types, this release introduces two additional approaches to produce an non-animated image from a multi-date request for colour-map (aka value_map) type styles:

1. Using a variant of the value_map_ entry used for the single-date case. This is a much simpler way of achieving most use cases.
2. Using an aggregator function, which allows for fully customisable behaviour but requires writing Python code.

The new behaviour is fully documented here: https://datacube-ows.readthedocs.io/en/latest/cfg_colourmap_styles.html#multi-date-requests

This means that OWS now supports rich comparison visualisation techniques for both contiguous and discrete data products.

Also, the masking rule parser for pq_masks sections now uses the same code as the parser for value_map rules in colour map styles.

This means that:

1. pq_mask rules now supports and/or operators, consistent with value_map rules.
2. value_map rules now support the invert operator, consistent with pq_mask rules.
3. The old "enum" keyword in pq_masks is now deprecated - please now use the values keyword, as in value_maps.

Full details are in the documentation. Old style syntax will continue to work as before - except the enum keyword in pq_masks now produces a deprecated warning message.

Changes in this release:

New Feature:

• Support for non-animated multi-date handlers for "colour-map" type styles. (#770)
• Consistent syntax for masking rules in pq_masks and value_map rules (#774)

Bug fixes

• Fix to bug affecting resource-limiting for WCS (#769)
• Fix bug in handling of missing data when applying cross-product masking (#772)

Dependency management and release process

• Remove constraint requiring very recent versions of numpy (#766)
• Upgrade to Postgis 3.1 (#767)
• Add automated spell check of documentation to github actions (#775)
• Increment default version number. (#776)

This release includes contributions from @Kirill888, @NikitaGandhi, @pindge and @SpacemanPaul