[Fixes #110] Feature: add metadata license to resource base

[mwallschlaeger]

Description

add metadata_license field to geonode metadata. Metadata_license shares available licenses with licenses (used for dataset licenses). Currently no default license is configured, as I thought this could be done via the upload-tool. The field is editable via the API:

,is part of the advanced metadata editor:

and part of the dataset configuration inside the admin panel:

Further licenses can be edited, deleted or added via the admin panel already.

Summarized CC-0 as default value is missing so far.

Type of Change

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• Bug fix
• New feature
• Documentation update
• Refactoring
• Other (please describe)

Related Issue

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closes #110

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