Add tags to LabRecord Imports

[manumoreira]

Add tags to categorize labrecord imports.
This tags will only be viewed and edited in the context of the store, none of this will be synchronized to the collector

[manumoreira]

This will require to enable edition for LabRecordImport it is critical to avoid enabling the deletion of LabRecordImports

[lmatayoshi]

Break down:

• Add tags table and model
• Add intermediate LabRecordImportTags table
• Enable Tags section in ActiveAdmin with Index, New, Edit and Delete
• Enable Edit interaction for LabRecordImports, which will allow only to add/remove tags

Details:

Tags table

id integer
name string

LabRecordImportsTags table

lab_record_imports_tags
lab_record_id integer
tag_id integer

[lmatayoshi]

@mmuller changes are listed in instedd/maap-store#88 (comment)

Let's test this by creating some tags, editing and deleting some few, and then going to the Lab Record Import list and adding tags to some imports.

Check permissions along the way: You should be able to perform any of the aforementioned actions as admin, whereas you shouldn't be able neither to see nor perform any modifying action as viewer.

Dropdown in Edit tags view is a standard select multiple HTML component with a pretty basic CSS and that's OK. We didn't want to spend much time styling it. However, what we should double check is the functionality. Tags that already belong to the LRI should start as selected, and you have to be able to select and deselect tags freely.