Add rds full disk space

[vmercierfr]

Objective

Add alert for RDS instance with full disk space

Why

RDS instance with full disk space requires immediate action to recover

How

• Move instructions to increase RDS storage to shortcodes to be reused
• Add RDSFullDiskSpace runbook
• Add RDSFullDiskSpace alert

Release plan

Release new minor version

[qfritz]

Why is this one needed in addition to RDSDiskSpaceLimit and RDSDiskSpacePrediction?

[vmercierfr]

These alerts are quite similar, but relevant because :

• RDSDiskSpaceLimit is a warning severity, and may be disabled
• RDSDiskSpacePrediction is critical but on write intensive workload, prediction could be received after storage full or severity could be overrided to warning by convention (service is not broken)
• RDSFullDiskSpace is critical provides a straight forward remediation instructions as there is not other option than scale. Just by looking at titleFullDiskSpace, on call engineers will have better understanding of situation