Add web/cli hook system for CRUD operations in objects

[Slach]

it will really usefull feature, which can integrate glauth with any external system or tools in config it may look like:

[[hooks]]
name = "disable github user when delete"
watchDN = "dc=glauth,dc=com,ou=example,github_login,github_orgs" 

# to cli hook will passed path as "dc=xx,dc=xxx, ..." operation like a "create \ delete \ update" operation params like a "key=value,key2=value2" format 
cli_hook = "some_cli_command ${PATH} ${OPERATION} ${OPERATION_PARAMETERS}"

# to web hook will passed POST http request with json format look like 
# {"source":"glauth", "path": "xxx", "operation": "create", "params": {"key":"value","key2":"value2" }
web_hook = "https://someadd/webhook"

i see multiple use cases for this feature:

• remove github\bitbucket user from organization when user blocked in ldap
• disable gmail\aws\gcloud\azure user when use blocked in ldap
• administator can add request to Vault secrets and approve them
• notify to adminitstator when someone block \ delete user who has access to some sensitive Vault secrets

Currently OpenLDAP, FreeIPA doesn't implement this feature