Ensure that the capacity endpoints are all working properly in swatch-contracts.

This includes at minimum the following, others may be discovered during the process. 

/v1/capacity/products/{product_id}/{metric_id}

IQE tests that need to be copied/redone for swatch-contracts: https://gitlab.cee.redhat.com/insights-qe/iqe-rhsm-subscriptions-plugin/-/blob/master/iqe_rhsm_subscriptions/conf/rhsm_subscriptions.default.yaml?ref_type=heads#L246

Done Criteria

• Capacity endpoints in swatch-contracts are able to be hit directly
• Existing swatch-api endpoints are not changed
• tests exist for that check capacity directly via swatch contracts without going through swatch-api