IdentifierAssignment plugin with minimum length and UTF-8 conversion

This feature has been requested by ACCESS CI (https://access-ci.org/) .

ACCESS IDs used by RPs (resource providers) should adhere to the following parameters:

• Minimum length: 3
• Maximum length: 32
• Character set: [a-zA-Z0-9]

Currently, https://registry.access-ci.org/ uses the following "Format" for ACCESS ID Identifier Assignment. This format is insufficient for our needs.

(g:1)(f)[1:(#)]

We have had issues with the following users:

1. Single letter for last name: e.g., "Julia K" resulted in ACCESS ID "jk"
2. UTF-8 only characters for first/last name: e.g., "숭동l이" resulted in ACCESS ID "1"
3. Very long last name: "Kapila Elkaduwe Rajapaksha Karunadhipathi Wasala H. M." resulted in ACCESS ID "krajapakshakarunadhipathiwasalahm"

A custom IdentifierAssignment plugin could handle the requirements of ACCESS CI RPs.

Related: CO-454 - "Identifier Assignment Does Not Support UTF-8 Characters"

Issue tracked by CILogon as CIL-1763.