Add Okta as identity provider. (#254)

diagrams/saas/identity.py

@@ -12,4 +12,8 @@ class Auth0(_Identity):
     _icon = "auth0.png"
 
 
+class Okta(_Identity):
+    _icon = "okta.png"
+
+
 # Aliases

docs/nodes/saas.md

@@ -27,6 +27,7 @@ Node classes list of saas provider.
 ## saas.identity
 
 - **diagrams.saas.identity.Auth0**
+- **diagrams.saas.identity.Okta**
 
 ## saas.logging