Delete a tag. Posts, ideas and content items carrying it are kept — the tag is removed from them.
The deletion cannot be undone. Requires the `posts:write` scope.

```graphql
mutation DeleteTag {
  deleteTag(input: {
    id: "some_tag_id"
  }) {
    ... on DeleteTagActionSuccess {
      id
    }
    ... on MutationError {
      message
    }
  }
}
```