Ansible deploy multiple authorized_keys on multiple hosts

We need deploy keys on the servers, but trick is that the keys are many and do not all of them must have deploy on all servers. Now we do it follows:

in vars roles/authorized_keys/vars/main.yml

ssh_users:
  - name: bob
    key: "{{ lookup('file', 'roles/authorized_keys/vars/bob.pub') }}" 
    state: present
  - name: root
    key: "{{ lookup('file', 'roles/authorized_keys/vars/guru.pub') }}"
    state: present
  - name: root
    key: "{{ lookup('file', 'roles/authorized_keys/vars/user.pub') }}"
    state: absent

in task: roles/authorized_keys/tasks/main.yml

- name: Add ssh key.
    authorized_key: user={{ item.name }} key="{{ item.key }}" state={{ item.state }}
    with_items: ssh_users

in playbook: authorized_keys.yml

---
- hosts: '{{ hosts }}'
  vars_files:
    - '{{ vars }}'
  roles:
    - { role: authorized_keys }

Before start playbook change roles/authorized_keys/vars/main.yml (present or absent). When start playbook add hosts and hosts group:

ansible-playbook -i production --extra-vars "hosts=web:pg:1.2.3.4" authorized_keys.yml

Previously, it was all good, but now increased the number of keys and servers. And now I do not remember whose key is to be on what server.

Tell me please how I can set up the list of hosts for each key? For example something like this:

- name: bob
    key: "{{ lookup('file', 'roles/authorized_keys/vars/bob.pub') }}" 
    servers: web,database,12.12.12.12
    state: present
- name: root
    key: "{{ lookup('file', 'roles/authorized_keys/vars/guru.pub') }}"
    servers: api,pg,30.30.30.30
    state: present