Allow default backup

[tamalsaha]

We could mark a Restic object as default. If a deployment does not have a specific Restic match, it will be use this default Restic to perform backup.

This will give user's default opt-in to backup ability. If they want to opt-out, they can pause their specific Restic or mark deployments will pause annotation.

[tamalsaha]

From @arjunsbabu via slack,

for default restic there are some issues i guess:

1. Deployments have different mount points for PV.So a single restic deployment cannot use for all workloads
2. all deployments dont need backup..If custiemr ask for backup then only we need to implement it

[tamalsaha]

• One option will be to create RsticTemplate that can be filled in via annotations from the Deployment.

• Non namespaced templates will allow backup for any new deployment using a label backup_required: true . Cluster administrator can create a library for ResticTemplates for various types of workloads.

[arjunsbabu]

@tamalsaha if possible can you give an example template

[tamalsaha]

https://appscode.slack.com/archives/DAFPBQP6Z/p1536068077000100

[hossainemruz]

Default backup is supported in v1beta1 design. It requires one BackupConfigurationTemplate that specifies template for Repository and BackupConfiguration crd and some annotations in workload that will be backed up.

v1beta1 design discussion: #648

Reference PRs: #647 #674 #675