ERROR cannot add subnet: subnet with CIDR "10.10.0.0/24" not found

[Impact]

According to the documentation https://juju.is/docs/olm/network-spaces the openstack provider supports spaces, although when trying to run "juju add-space" there is an error, and for the case of "juju reload-spaces" the subnets are not pulled into juju's database.

Here it's an example of what happens when trying to create a space associated to the subnet "ironic_subnet" with the CIDR 10.10.0.0/24

$ openstack subnet list
+--------------------------------------+---------------------+--------------------------------------+--------------+
| ID | Name | Network | Subnet |
+--------------------------------------+---------------------+--------------------------------------+--------------+
| 2bb6e419-c559-4e0a-9575-4bb135349254 | freyes_admin_subnet | 27cc5fef-a820-4ddc-a426-58e2aeb98dcc | 10.5.0.0/16 |
| 6e5beb18-e5e3-4201-aa6f-bfc21a0376fb | ironic_subnet | ccf908c7-cdd9-45b5-aa35-d5de2a48b4c5 | 10.10.0.0/24 |
+--------------------------------------+---------------------+--------------------------------------+--------------+
$ juju spaces
Name Space ID Subnets
alpha 0 10.5.0.0/16

$ juju models
Controller: serverstack

Model Cloud/Region Type Status Machines Cores Units Access Last connection
controller* serverstack/serverstack openstack available 1 2 1 admin just now
default serverstack/serverstack openstack available 0 - - admin 1 hour ago

$ juju add-subnet 10.10.0.0/24 ironic-space
ERROR cannot add subnet: subnet with CIDR "10.10.0.0/24" not found
$ juju reload-spaces
$ juju spaces
Name Space ID Subnets
alpha 0 10.5.0.0/16
                 252.0.0.0/8

$ snap info juju | grep installed
installed: 3.0-beta1-acfa032 (16965) 91MB classic

Note: this behavior could be reproduced using juju 2.8, 2.9 and 3.0-beta1-acfa032 (latest/edge).