Keycloak - Assign User to group from registration form - keycloak

Question

I'm trying to create a custom registration form in Keycloak that will create the user and assign them to a group depending on a team drop down selection. Here is an example of my problem:
I have multiple teams that will be using keycloak and each team will have their own group in keycloak mapping out all the roles that they need access to. One app that will be using keycloak authentication is Grafana. When a user goes to Grafana and tries to register for a new account via keycloak, it creates the user, but because the user isn't assigned to a group, they land at an error page in Grafana because they don't have any privilege.
I'm trying to limit the amount of manual work to assign hundreds of users to groups after they register. I don't have access to LDAP or Active Directroy.
Here is an example of what i've tried in my custom register.ftl template.
<div class="${properties.kcFormGroupClass!} ${messagesPerField.printIfExists('team',properties.kcFormGroupErrorClass!)}">
<div class="${properties.kcLabelWrapperClass!}">
<label for="groups" class="${properties.kcLabelClass!}">Team</label>
</div>
<div class="${properties.kcInputWrapperClass!}">
<select class="${properties.kcInputClass!}" id="groups" name="groups" value="${(register.formData['groups']!'')}">
<option value="group1">Group 1</option>
<option value="group2">Group 2</option>
<option value="group3">Group 3</option>
</select>
</div>
</div>
I was successfully able to add the group as a user attribute, and then thought I could execute a script after that uses the rest API to then assign the group, but I haven't had much luck with that either. I would like to stay away from assigning everyone to a default "view only" group because some groups don't need to be able to view all the apps that we will use.
If anyone has any ideas or could help point me in the right direction, please let me know. I have limited knowledge HTML & Javascript but know my way around Python.