feat(vault): allow passing down VAULT_SKIP_VERIFY

[aslafy-z]

Description

Allow disabling Vault SSL validation.

Related Issue

Fixes #49

Motivation and Context

This allows disabling SSL verification when working with non-trusted self-signed certificates when prototyping.

How Has This Been Tested?

• Set VAULT_ADDR to a self-signed non trusted certificate backed vault instance
• Set VAULT_SKIP_VERIFY=false
• Run himl with a vault secret
• Raises with error: requests.exceptions.SSLError: HTTPSConnectionPool(host='vault.xx.com', port=443): Max retries exceeded with url: /v1/auth/token/lookup-self (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1125)')))
• Current functionnality is retained

================

• Set VAULT_ADDR to a self-signed non trusted certificate backed vault instance
• Set VAULT_SKIP_VERIFY=true
• Run himl with a vault secret
• Works
• Current functionnality is retained

================

• Set VAULT_ADDR to a self-signed trusted certificate backed vault instance
• Run himl with a vault secret
• Works
• Current functionnality is retained

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.