Make configurable the maximum qos that a server can handle

[andsel]

Release notes

Exposed the maximum granted QoS by the server with the config setting 'max_server_granted_qos'.

What does this PR do?

Updates the PostOffice when process the subscribe message to cap the QoS that the server would handle.

Why is it important/What is the impact to the user?

Permit to the user to limit the capabilities of the server to limit the support qos level.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files (and/or docker env variables)
• [ ] I have added tests that prove my fix is effective or that my feature works
• I have updated the Changelog if it's a feature or a fix that has to be reported

A

Related issues

• Relates Implements Subscription Options #808