changing the boolean config option does not configure the snap-openstack-hypervisor correctly

[Chi Wai CHAN]

Currently, the config data flows from charm to snap.

In the charm, the config option for boolean type (`debug` and `enable-gateway`) will be set to a string of "true" or "false" in the snap configuration using `operator.libs.linux (snap.py)` [1,2]. Then, in the snap, the config option will be also read as a string using `snaphelper`. However, the snap is using the config option as a boolean type [3] which always return `True` for non empty string. For example, one checks the `hooks.log`:

```
# in /var/snap/openstack-hypervisor/common/hooks.log

09:58:57,671 root WARNING Context {'compute': {'cpu_mode': 'host-model', 'spice_proxy_address': '10.6.0.77', 'virt_type': 'kvm'}, 'credentials': {'ovn_metadata_proxy_shared_secret': '0JF9pzVFi0WF64YPG8erHaBLguDkJMBv'}, 'identity': {'admin_role': 'Admin', 'auth_url': 'http://10.6.0.202:80/openstack-keystone', 'password': 'RTEa5Jlfra3h', 'project_domain_id': 'c582aeb94a484553b898faa2d4d27cec', 'project_domain_name': 'service_domain', 'project_name': 'services', 'region_name': 'RegionOne', 'user_domain_id': 'c582aeb94a484553b898faa2d4d27cec', 'user_domain_name': 'service_domain', 'username': 'openstack-hypervisor'}, 'logging': {'debug': 'true'}, 'network': {'dns_domain': 'openstack.local', 'dns_servers': '8.8.8.8', 'enable_gateway': 'false', 'external_bridge': 'br-ex', 'external_bridge_address': '10.20.20.1/24', 'ip_address': '10.6.0.77', 'ovn_cacert': '<too_long>', 'ovn_cert': '<too_long>', 'ovn_key': '<too_long>', 'ovn_sb_connection': 'ssl:10.6.0.200:6642', 'physnet_name': 'physnet1'}, 'node': {'fqdn': 'sunbeam01.project.serverstack', 'ip_address': '10.6.0.77'}, 'rabbitmq': {'url': 'rabbit://hypervisor:Sbh9BxXQ1Ksr@10.6.0.201:5672/openstack'}, 'snap_common': '/var/snap/openstack-hypervisor/common', 'snap_data': '/var/snap/openstack-hypervisor/x10', 'snap': '/snap/openstack-hypervisor/x10'}
09:58:57,671 root WARNING [] are missing required config, stopping
09:58:57,833 root INFO Rendering /var/snap/openstack-hypervisor/common/etc/nova/nova.conf
09:58:57,846 root INFO Rendering /var/snap/openstack-hypervisor/common/etc/neutron/neutron.conf
09:58:57,852 root INFO Rendering /var/snap/openstack-hypervisor/common/etc/neutron/neutron_ovn_metadata_agent.ini
09:58:57,858 root INFO Rendering /var/snap/openstack-hypervisor/common/etc/libvirt/libvirtd.conf
09:58:57,860 root INFO Rendering /var/snap/openstack-hypervisor/common/etc/libvirt/qemu.conf
09:58:57,862 root INFO Rendering /var/snap/openstack-hypervisor/common/etc/libvirt/virtlogd.conf
09:58:57,863 root INFO Rendering /var/snap/openstack-hypervisor/common/etc/openvswitch/system-id.conf
09:58:58,13 root INFO Configuring Open vSwitch geneve tunnels and system id. ovn-encap-ip = 10.6.0.77, system-id = sunbeam01.project.serverstack
09:58:58,143 root INFO configuring external bridge br-ex
09:58:58,143 root DEBUG Adding ip 10.20.20.1/24 to br-ex
09:58:58,148 root DEBUG ['iptables-legacy', '--check', 'POSTROUTING', '-w', '-t', 'nat', '-s', '10.20.20.0/24', '-j', 'MASQUERADE', '-m', 'comment', '--comment', 'openstack-hypervisor external network rule']
09:58:58,152 root DEBUG Found existing postrouting rule for 10.20.20.0/24
09:58:58,165 root INFO Enabling OVS as external gateway
09:58:58,266 root INFO Checking virtualization extensions presence on the host
09:58:58,278 root INFO Hardware virtualization is supported - KVM will be used.
```

Notice that even though {'enable_gateway': 'false'}, it still outputs the "INFO Enabling OVS as external gateway".

The root cause may be related to the issue in `operator.libs.linux (snap.py)` [4]

[1] https://opendev.org/openstack/charm-openstack-hypervisor/src/branch/main/src/charm.py#L145
[2] https://opendev.org/openstack/charm-openstack-hypervisor/src/branch/main/lib/charms/operator_libs_linux/v2/snap.py#L327
[3] https://github.com/openstack-snaps/snap-openstack-hypervisor/blob/main/openstack_hypervisor/hooks.py#L740
[4] https://github.com/canonical/operator-libs-linux/issues/107

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: main
Review: https://review.opendev.org/c/openstack/charm-openstack-hypervisor/+/893313

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-openstack-hypervisor/+/893313
Committed: https://opendev.org/openstack/charm-openstack-hypervisor/commit/42ec5b1412c3fd9b90fbf256b1a054a07ec16189
Submitter: "Zuul (22348)"
Branch: main

commit 42ec5b1412c3fd9b90fbf256b1a054a07ec16189
Author: Chi Wai Chan <email address hidden>
Date: Wed Aug 30 18:08:37 2023 +0800

    Fix the typing issue in snap configs.

    Currently, setting boolean config with `Snap.set` will result in setting
    the snap config to a string of `true` or `false`, and the openstack
    hypervisor snap will read those configs as string as well. This makes
    the condition checking in openstack-hypervisor snap behaves incorrectly
    [1]. This PR is to update the snap library will proper typing support.

    - Update snap library
    - Fix the data types used in `Snap.set()`

    [1] https://github.com/openstack-snaps/snap-openstack-hypervisor/blob/main/openstack_hypervisor/hooks.py#L740

    Closes-Bug: #2033272
    Change-Id: I7bec4599b23500aaad9e008fce648793c104b642