Add categories to initiatives

Is your feature request related to a problem? Please describe.

Initiatives cannot be categorized as proposals.

Describe the solution you'd like

As an admin, I want to be able to link categories to initiatives.

Allow admin to create, edit & destroy categories in an index (see mockup below).

• This index must be available by clicking under the initative_type button in admin secondary navbar.
• You can't destroy a category if it's linked to an initiative
• This index is only visible for admins.

Add a /new and /edit form to be able to create or edit a category

Allow admin to link a category to an initiative

• Add a dropdown field on the /edit form of initiatives that displays all the categories created.
• Permissions : The category field is only displayed for admins. Users can't see it nor edit it.
• When the initiative is updated, the category will be displayed automatically on initiative card & show in FO (see below)

Allow users to see categories & filter the index

• The title should appear as a link under the description of the initiative
• When clicking on the category title, index is filtered to only display the initiatives linked to this category (same as scopes & categories)

Allow users to see categories on initiative show & filter the index

• The category title should be displayed as a link under the description of the initiative
• When clicking on the category title, the user is redirected to a filtered index that only displays the initiatives linked to this category

Describe alternatives you've considered

None

Does this issue could impact on users private data?

No