Implement Gtk Network Status (#165)

Implemented
- Switch reacts to burrow socket and network changes 
- meson as build system
- Basic diagnostics to ensure burrow is installed properly
- Flatpak / Meson Building

burrow-gtk/src/diag.rs

@@ -0,0 +1,80 @@
+use super::*;
+use std::{fmt::Display, fs, process::Command};
+
+const SYSTEMD_SOCKET_LOC: &str = "/etc/systemd/system/burrow.socket";
+const SYSTEMD_SERVICE_LOC: &str = "/etc/systemd/system/burrow.service";
+
+//  I don't like this type very much.
+#[derive(Debug, Clone, Copy)]
+pub enum StatusTernary {
+    True,
+    False,
+    NA,
+}
+
+//  Realistically, we may not explicitly "support" non-systemd platforms which would simply this
+//  code greatly.
+//  Along with replacing [`StatusTernary`] with good old [`bool`].
+#[derive(Debug, Clone, Copy)]
+pub enum SystemSetup {
+    Systemd,
+    Other,
+}
+
+impl SystemSetup {
+    pub fn new() -> Self {
+        if Command::new("systemctl").arg("--version").output().is_ok() {
+            SystemSetup::Systemd
+        } else {
+            SystemSetup::Other
+        }
+    }
+
+    pub fn is_service_installed(&self) -> Result<StatusTernary> {
+        match self {
+            SystemSetup::Systemd => Ok(fs::metadata(SYSTEMD_SERVICE_LOC).is_ok().into()),
+            SystemSetup::Other => Ok(StatusTernary::NA),
+        }
+    }
+
+    pub fn is_socket_installed(&self) -> Result<StatusTernary> {
+        match self {
+            SystemSetup::Systemd => Ok(fs::metadata(SYSTEMD_SOCKET_LOC).is_ok().into()),
+            SystemSetup::Other => Ok(StatusTernary::NA),
+        }
+    }
+
+    pub fn is_socket_enabled(&self) -> Result<StatusTernary> {
+        match self {
+            SystemSetup::Systemd => {
+                let output = Command::new("systemctl")
+                    .arg("is-enabled")
+                    .arg("burrow.socket")
+                    .output()?
+                    .stdout;
+                let output = String::from_utf8(output)?;
+                Ok((output == "enabled\n").into())
+            }
+            SystemSetup::Other => Ok(StatusTernary::NA),
+        }
+    }
+}
+
+impl From<bool> for StatusTernary {
+    fn from(value: bool) -> Self {
+        if value {
+            StatusTernary::True
+        } else {
+            StatusTernary::False
+        }
+    }
+}
+
+impl Display for SystemSetup {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(match self {
+            SystemSetup::Systemd => "Systemd",
+            SystemSetup::Other => "Other",
+        })
+    }
+}