3scale alerts SOPs

As part of the 3scale Managed Service and the recent 3scale monitoring, we (SRE/Ops team) have created an initial version of the SOP (Standard Operating Procedures) for the 3scale alerts added on 3scale 2.9. These SOPs will be linked to the prometheus alerts created by the operator, so in case an SRE is paged by an alert, they have the needed context and help to fix the problem, what to check...

They can be found at https://github.com/3scale/3scale-Operations/tree/master/sops/alerts

Add an annotation "sop_url" to every alert with the corresponding link to github