Apply templates to the TileMatrixSets and TileMatrixSet resources.

[doublebyte1]

Overview

Unlike other endpoints, the TileMatrixSets and TileMatrixSet endpoints don't have a dataset associated and thus this call is not applied:

tpl_config = api.get_dataset_templates(dataset)

Instead, the entire API configuration (api.tpl_config) is passed as the template configuration. As it fails it falls back to default template, ignoring the custom theme. This PR fixes that, by explicitly applying the templates.

Related Issue / discussion

#2422

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