terraform plan (check-tf-consistency) modification thresholds for on-demand services

[gberche-orange]

Is your feature request related to a problem? Please describe.

On demand services, such as cloudflare-depls don't currently include a terraform plan step (ie the check-tf-consistency pipelines which requires systematic manual approval). When configuration problems occur which modify a large proportion of entries, then this large modification is still applied without operator confirmation.

Such support could also solve #139

Describe the solution you'd like

A systematic terraform plan step which only requires manual approval when both conditions below are met:

• a minimal number of entries are deleted/modified
• a minimal percent of entries are deleted/modified

Describe alternatives you've considered

• during risky steps (such as Iaas migration), restore a systematic manual validation step
  • e.g. through configuration in secrets repo
  • through a local modification such as Document how template authors can reexecute their jobs with locally patch scripts #182

Additional context
Add any other context or screenshots about the feature request here.