Add Section on Node/Agbot Token Requirements

[Rene-Ch1]

Add the subject section to https://github.com/open-horizon/open-horizon.github.io/blob/master/docs/user_management/security_privacy.md.

Add a trimmed down version of the following as an FYI in https://www.ibm.com/docs/en/eam/4.3?topic=security-privacy#agents; the file source is here in the OH repo: https://github.com/open-horizon/open-horizon.github.io/blob/master/docs/user_management/security_privacy.md.

The Exchange recently added some minimum requirements for all Node and Agbot tokens.
The requirements are as follows:

• a digit must occur at least once
• a minimum of 15 chars
• at least one uppercase letter
• at least one lowercase letter

For Korean, Japanese, and Chinese the requirements are:

• a digit must occur at least once
• a minimum of 15 chars

Ben Courliss 3:11 PM
I don't think that's the right place. If you were to include a FYI section, I'd recommend here https://www.ibm.com/docs/en/eam/4.3?topic=security-privacy#agents. Specifically after this Each node has unique credentials that are stored in its own root protected storage. The Horizon exchange ensures that a node can only access its own resources. But as it's worded by Sadiyah, it's too verbose.

The origin for this issue is in the IEAM repo here.