Enable integration of components on test+development machines

[abeltrano]

Type

• Bug fix
• Feature addition
• Feature update
• Documentation
• Build Infrastructure

Side Effects

• Breaking change
• Non-functional change

Goals

• Ease testing on development machine.
• Enable sandboxing testing components.

Technical Details

• Add templated systemd service unit file for hostapd which parameterizes the wlan interface (eg. systemctl enable hostapd@wlan0).
• Remove non-templated system service unit file for hostapd. This form is unlikely to be used since it hardcodes the wlan interface name and would require interface renaming logic on the server system, introducing complexity and some races.
• Install the hostapd binary and libwpa_client.so shared object library.
• Rename example hostapd.conf to hostapd.example.conf to make clear that it's an example file.
• Add comments to hostapd.example.conf describing the modifications needed to use it with an instantiated systemd service unit.
• Add network device subsystem requirement and sequencing directives in the hostapd systemd service unit template, to ensure the network subsystem is ready before starting the hostapd daemon.
• Append wlan interface name to hostapd pid file to help differentiate ownership.
• Use full paths for install locations in configure-files to allow use of project artifacts.

Test Results

• Validated filesystem tree for cmake --install is as expected.
• Validated configured files, hostapd@.service and hostapd.example.conf reference correct paths.

Reviewer Focus

• None

Future Work

• Consider authoring a script which installs the systemd service unit files for production.

Checklist

• Build target all compiles cleanly.
• clang-format and clang-tidy deltas produced no new output.
• Newly added functions include doxygen-style comment block.