Add logging to HTTPClient and Credentials

[sserrata]

• Palo Alto Networks Cloud Python SDK version: v1.3.0
• Python version: 2.7, 3.5+
• Operating System: any

Description

Although the underlying requests library is capable of low-level logging the pancloud HTTPClient and Credentials classes do not currently offer any additional logging to assist with troubleshooting and debugging.

Proposed solution

Add sensible logging to HTTPClient and Credentials classes for operations unique to pancloud, such as:

• Applying credentials to header
• Setting default headers
• Auto-refresh and auto-retry
• Token refresh
• Credential resolution
• Fetch tokens
• Initializing storage adapter
• Removing profiles
• Revoke access/refresh token
• Write credentials
• Checking for expired access token
• Decoding exp field from access token

[sserrata]

Sensible logging has been added to both HTTPClient and Credentials classes.