Add uncategorised cookie category

Replace the `required` boolean column on cookie_categories with a `kind`
enum (NORMAL, NECESSARY, UNCATEGORISED). The Necessary category remains
undeletable and always-on for consent; the new Uncategorised category is
also undeletable but users can opt out of it.

When a category is deleted, its cookies are merged into the Uncategorised
category (lazy-created for legacy banners that don't have one yet).

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/cookiebanner/errors.go

@@ -17,15 +17,15 @@ package cookiebanner
 import "errors"
 
 var (
-	ErrBannerNotFound               = errors.New("cookie banner not found")
-	ErrCategoryNotFound             = errors.New("cookie category not found")
-	ErrVersionNotFound              = errors.New("cookie banner version not found")
-	ErrBannerAlreadyActive          = errors.New("cookie banner is already active")
-	ErrBannerAlreadyInactive        = errors.New("cookie banner is already inactive")
-	ErrVersionNotPublished          = errors.New("cookie banner version is not published")
-	ErrNoPublishedVersion           = errors.New("no published cookie banner version")
-	ErrNoDraftVersion               = errors.New("no draft cookie banner version to publish")
-	ErrCannotDeleteRequiredCategory = errors.New("cannot delete required cookie category")
-	ErrOriginAlreadyInUse           = errors.New("origin is already used by another active cookie banner")
-	ErrConsentNotFound              = errors.New("consent record not found")
+	ErrBannerNotFound             = errors.New("cookie banner not found")
+	ErrCategoryNotFound           = errors.New("cookie category not found")
+	ErrVersionNotFound            = errors.New("cookie banner version not found")
+	ErrBannerAlreadyActive        = errors.New("cookie banner is already active")
+	ErrBannerAlreadyInactive      = errors.New("cookie banner is already inactive")
+	ErrVersionNotPublished        = errors.New("cookie banner version is not published")
+	ErrNoPublishedVersion         = errors.New("no published cookie banner version")
+	ErrNoDraftVersion             = errors.New("no draft cookie banner version to publish")
+	ErrCannotDeleteSystemCategory = errors.New("cannot delete system cookie category")
+	ErrOriginAlreadyInUse         = errors.New("origin is already used by another active cookie banner")
+	ErrConsentNotFound            = errors.New("consent record not found")
 )