DBaaS: Promote Portal Kubernetes cluster creation feature in PMM

Problem:

Percona Portal team implemented provisioning of K8s cluster to simplify testing of DBaaS feature in PMM. We need to make sure that PMM users have information about the availability of the free K8s cluster on Percona Portal which can help them to discover the PMM DBaaS feature.

Acceptance criteria:

• DBaaS functionality mentions that users now can create K8s clusters on Percona Portal. 
• The feature is available for all registered accounts with a limit of 1 cluster per day, per user and cluster availability for 3h. This should be enough for testing puproses. 

UX:

Link - need to be controllable by Percona, so when the Promo is done  -we'll route it to another  page 

Implementation:

 TBD  

Details:

https://jira.percona.com/browse/SAAS-916