CRUD for tags (only Read)

[chargio]

As a user, I want to be able to create new tags.

All tags will be lowercase.

• It should not be possible to create new tags in the interface. Tags should be automatically created when assigning them or creating the spin with tags
• it should not be possible to update a tag. Updating a tag would mean creating a new one and a new association.
• Tags should be destroyed when there are no taggins associatied to them
• It should be possible to show a tag