[3.3.x] [Fixes #8690] Custom filters available for the “ResourceBase” opaque filters

[mattiagiupponi]

Refers to #8690

• Add base_tag to handle the dynamic creation of facets for dynamic metadata
• add HTML for handle the metadata
• bugfix on metadata search for tastypie

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[lgtm-com]

This pull request introduces 1 alert when merging 79ae119 into 72740ed - view on LGTM.com

new alerts:

• 1 for Unused import

[mattiagiupponi]

@afabiani Documentation PR is available here GeoNode/documentation#220