fix: more info about automatic user authentication/hyperforce/jwt (#860)

Author: jshackell-sfdc

messages/create.md

@@ -19,6 +19,8 @@ Use the --set-alias flag to assign a simple name to the user that you can refere
 
 When this command completes, it displays the new username and user ID. Run the "org display user" command to get more information about the new user.
 
+After the new user has been created, Salesforce CLI automatically authenticates it to the scratch org so the new user can immediately start using the scratch org. The CLI uses the same authentication method that was used on the associated Dev Hub org. Due to Hyperforce limitations, the scratch org user creation fails if the Dev Hub authentication used the JWT flow and the scratch org is on Hyperforce. For this reason, if you plan to create scratch org users, authenticate to the Dev Hub org with either the "org login web" or "org login sfdx-url" command, and not "org login jwt".
+
 For more information about user limits, defaults, and other considerations when creating a new scratch org user, see https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_scratch_orgs_users.htm.
 
 # examples