post https://a.klaviyo.com/api/tags/
Create a tag. An account cannot have more than 500 unique tags.
A tag belongs to a single tag group. If the tag_group_id is not specified,
the tag is added to the account's default tag group.
Rate limits:
Burst: 3/s
Steady: 60/m
Scopes:
tags:read
tags:write