Add file encrypting functionality "yaml.j2" --> "yaml.j2.enc" files via a wrapper

[mldev94]

#125 - Related to this issue but this PR technically not happening in-memory. That requires closer integration with k8t but this still works.

What is this?

This lets you use encrypted "yaml.j2" files with the "k8t" tool.
Encrypted files stay encrypted while the data is at-rest.
This is helpful for pushing your k8t project on GitHub while including all your encrypted secrets.

How it works?

"./k8tsecure" is a wrapper for "k8t".
It takes the same arguments as k8t.
Before running the actual k8t command, it decrypts all encrypted YAML files using "ansible-vault".
Then, runs the k8t command with those temporarily decrypted files.
When the k8t command is completed, it discards the temporarily decrypted YAML files.

That keeps your git-working tree clean.
None of the decrypted files end up accidentally being committed to the git repository.

Requirements

This utilizes "ansible-vault" command for encryption and decryption:
https://docs.ansible.com/ansible/latest/vault_guide/index.html

It requires one of the following installations

• Official: The entire ansible installation including "ansible-vault"
  Link: https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html
• Unofficial: There is a github project containing only the "ansible-vault" command/slimmed-down version of Ansible
  Link: https://pypi.org/project/ansible-vault/

How-to-use this?

1. Create an empty "ansible.cfg" file in the same directory as this script(root of the k8t project)

2. Add the following two lines without the "#"s in that config file and update the password file's location based on your needs. Preferably, it should be outside of the git repository directory. You could use your home directory, etc.

   [defaults]
   vault_password_file = ./some_directory/.vault_password.txt 

3. open that ./some_directory/.vault_password.txt file
   and add the desired password (e.g. 16 characters)

4. rename any file that you want to encrypt by following the name convention below.
   some-secret.yaml.j2 --> some-secret.yaml.j2.enc
   another.yaml.j2 --> another.yaml.j2.enc

5. run "./k8tsecure encrypt_all" once to encrypt all the .enc files for first-time setup.

6. From that point, everytime you want to use "k8t" tool,
   use "./k8tsecure" instead. k8tsecure encapsulates k8t behind the scenes while handling the encrypted files.
   The arguments/flags are the same as "k8t" tool's original command-set due to the encapsulation

   "k8t gen --environment development > compiled_dev_environment.yaml"
   becomes
   "./k8tsecure gen --environment development > compiled_dev_environment.yaml"

7. Anytime you need to edit those ".enc" files,
   run the standard "ansible-vault" commands from directory where you have "ansible.cfg" file.
   e.g. "ansible-vault edit some-secret.yaml.j2.enc"

8. Available options for k8tsecure
   "./k8tsecure encrypt_all" -- Encrypts all files containing ".enc" in the filename
   "./k8tsecure decrypt_all" -- Decrypts all files containing ".enc" in the filename
   "./k8tsecure any k8t flag option etc." -- Passes through all the arguments to k8t after temporarily decrypting the ".enc" files.