Add ability to configure Postgres backups

[ndarilek]

Change Summary

• Adds a fly pg backup config subcommand with ability to show and update backup-related configuration values
• Adds and refactors to helpers to run commands on Postgres machines or the cluster leader

nolan@nolan-fly:~/flyctl$ go run . pg backup config help                                                                
Manage backup configuration                                                                                             
                                                                                                                        
Usage:                                                                                                                  
  fly postgres backup config [command]                                                                                  
                                                                                                                        
Available Commands:                                                                                                     
  show        Show backup configuration                                                                                 
  update      Update backup configuration                                                                               
                                                                                                                        
Flags:                                                                                                                  
  -h, --help   help for config                                                                                          
                                                                                                                        
Global Flags:                                                                                                           
  -t, --access-token string   Fly API Access Token                                                                      
      --debug                 Print additional logs and traces                                                          
      --verbose               Verbose output                                                                            
                                                                                                                        
Use "fly postgres backup config [command] --help" for more information about a command.                                 
nolan@nolan-fly:~/flyctl$ go run . pg backup config show -a nolan-pg                                                    
  ArchiveTimeout = 60s                                                                                                  
  RecoveryWindow = 7d                                                                                                   
  FullBackupFrequency = 24h                                                                                             
  MinimumRedundancy = 3                                                                                                 
nolan@nolan-fly:~/flyctl$ go run . pg backup config update -a nolan-pg --minimum-redundancy foo                         
Exit code: 1                                                                                                            
error updating configuration: invalid value for minimum_redundancy: foo                                                 
nolan@nolan-fly:~/flyctl$ go run . pg backup config update -a nolan-pg --minimum-redundancy 5                           
Updated                                                                                                                 
A restart is required for these changes to take effect. Run `fly app restart -a nolan-pg` to restart.)nolan@nolan-fly:~/flyctl$ go run . pg backup config show -a nolan-pg                                                                      
  ArchiveTimeout = 60s                                                                                                  
  RecoveryWindow = 7d                                                                                                   
  FullBackupFrequency = 24h                                                                                             
  MinimumRedundancy = 5                                                                                                 

Related to: fly-apps/postgres-flex#244

---

Documentation

• Fresh Produce
• In superfly/docs, or asked for help from docs team
• n/a

[davissp14]

This is fine, but unnecessary

[ndarilek]

Why not? Do we not want to block on versions like v0.0.53 with backup support but not backup config support? Happy to remove it but the UX when someone runs fly pg backup config wouldn't clarify how they fix it.

[davissp14]

Oh, sorry, I should have clarified. The version check is necessary, but abstracting it into a separate function isn't, since it's just issuing a return.

[davissp14]

Can we do the same thing here that we did below? Define the version as a constant and just reuse hasRequiredVersiononMachines ?

[davissp14]

Added a comment, but once that is fixed feel free to merge!

[davissp14]

Looks good!