Add description templates for user onboarding and offboarding

.gitlab/issue_templates/Offboard.md

+<!--
+This template should be used for offboarding Arch Linux team members.
+-->
+
+# Offboarding an Arch Linux team member
+
+## Details
+
+- **Team member username**:
+- **Currently held roles**: <!-- Add known roles here like TU, DevOps, etc -->
+
+## All roles checklist
+
+- [ ] Remove user email by reverting instructions from `docs/email.md`.
+- [ ] Set user to inactive in archweb: https://www.archlinux.org/admin/auth/user/
+
+## TU/Developer offboarding checklist
+
+- [ ] Remove entry in `group_vars/all/archusers.yml`.
+- [ ] Remove SSH pubkey from `pubkeys/<username>.pub`.
+- [ ] Run `ansible-playbook -t archusers playbooks/*.yml`.
+- [ ] Remove the user from the `Trusted Users`/`Developers` groups on Keycloak.
+
+## DevOps offboarding checklist
+
+- [ ] Remove entries in `group_vars/all/root_access.yml`.
+- [ ] Run `ansible-playbook -t root_ssh playbooks/*.yml`.
+- [ ] Run `ansible-playbook playbooks/hetzner_storagebox.yml playbooks/rsync.net.yml`.
+- [ ] Remove the user from the `DevOps` group on Keycloak.

.gitlab/issue_templates/Onboard.md

+<!--
+This template should be used for onboarding new Arch Linux team members.
+It can also be used as a reference for adding new roles to an existing team member.
+-->
+
+# Onboarding an Arch Linux team member
+
+## Details
+
+- **Team member username**:
+
+## All roles checklist
+
+- [ ] Add new user email as per `docs/email.md`.
+- [ ] Create a new user in archweb: https://www.archlinux.org/devel/newuser/
+      This is also linked in the django admin backend at the top
+
+## TU/Developer onboarding checklist
+
+- [ ] Add entry in `group_vars/all/archusers.yml`.
+- [ ] Add SSH pubkey to `pubkeys/<username>.pub`.
+- [ ] Run `ansible-playbook -t archusers playbooks/*.yml`.
+- [ ] Assign the user to the `Trusted Users`/`Developers` groups on Keycloak.
+
+## DevOps onboarding checklist
+
+- [ ] Add entries in `group_vars/all/root_access.yml`.
+- [ ] Run `ansible-playbook -t root_ssh playbooks/*.yml`.
+- [ ] Run `ansible-playbook playbooks/hetzner_storagebox.yml playbooks/rsync.net.yml`.
+- [ ] Assign the user to the `DevOps` group on Keycloak.

docs/users.md

-# Add a new dev/TU
-
- - Add the user to group_vars/all/archusers.yml
- - Copy the ssh key to pubkeys/$username.pub
-
- - Run `ansible-playbook -t archusers playbooks/*.yml` or similar
-
- - To create a new user in archweb use: https://www.archlinux.org/devel/newuser/
-   This is also linked in the django admin backend at the top
-
- - For email accounts refer to docs/email.txt