Use Secret instead of ConfigMap for pod env

[eberlep]

⚠️ Use Secret instead of ConfigMap for pod environment configuration -> triggers rolling update of running databases

[eberlep]

Tested successfully:

• Created database with old image: it's unsing a configmap
• Updated image
• Checked existing database:
  • configmap still existing, but new secret created.
  • k describe pod <DATABASE> refers to secret, not configmap
• Created new database:
  • no postgres-pod-config configmap, but a secret
  • k describe pod <DATABASE> refers to secret, not configmap

 $ k describe po pgfits-podenvsecretc79a3f32-0                                                                                                                                                                                                                                                  
Name:         pgfits-podenvsecretc79a3f32-0                                                                                                                                                                                                                                                                                                                                
Namespace:    b621eb9948884911-c79a3f32296a4d728099                                                                                                                                                                                                                                                                                                                        
[..]
Containers:                                                                                                                                                                                                                                                                                                                                                                
  postgres:                                                                                                                                                                                                                                                                                                                                                                
    [..]
    Environment:                                                                                                                                                                                                                                                                                                                                                           
      [..]
      AWS_ACCESS_KEY_ID:                 <set to the key 'AWS_ACCESS_KEY_ID' in secret 'postgres-pod-config'>        Optional: false```