Add early support for JSON-FG

[francbartoli]

Overview

This PR adds support to the most recent JSON-FG specification 0.3. It returns JSON-FG formatted payload with the following conformance classes:

• http://www.opengis.net/spec/json-fg-1/0.3/conf/core
• http://www.opengis.net/spec/json-fg-1/0.3/conf/types-schemas

A new formatter has been added to the core for that scope and must rely on GDAL>=3.12 which supports 0.3 (not yet released as of today). As a consequence, this is a breaking change for our dependencies chain and cannot be merged until rasterio will support that version as well.
This potentially might be relaxed after the merge of this branch https://github.com/geopython/pygeoapi/tree/formatters to have the formatter configurable at resource level and so the GDAL requirement needed only if it is configured.

Related Issue / discussion

• Configurable formatter

Additional information

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
• https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[webb-ben]

How does this provider differ from a (generic) GDAL based formatter capable of formatting to any OGR data type?

[francbartoli]

It is very close potentially, what are you imaging?

[webb-ben]

Well once you read it into GDAL, any vector driver transform can occur. Wondering if would be possible to make any output format in the same spirit of the OGR provider - formatter config only barrier to add Shapefile, KML, etc. as an output format for pygeoapi GeoJSON.

[github-actions]

This Pull Request has been inactive for 90 days. As per RFC4, in order to manage maintenance burden, it will be automatically closed in 7 days.

[tomkralidis]

@francbartoli given #2144 looks like this can be now implemented as a standalone formatter. Are you able to update accordingly?

[tomkralidis]

pygeoapi meeting 2026-05-15

• updating to GDAL 3.12 will facilitate JSON-FG output support
• needs packaging (@kalxas to review)
• consider dependencies/requirements in core (may be a moot point given rasterio is required).