Break up code into multiple files

In order to increase readability, maintainability and maybe a future
independence regarding web frameworks move code to new files.

src/cli.rs

@@ -0,0 +1,22 @@
+use clap::{crate_authors, crate_version, AppSettings, Parser};
+
+#[derive(Debug, Parser)]
+pub enum Command {
+    /// Verifies if the configuration can be parsed without errors
+    Configtest,
+}
+
+#[derive(Debug, Parser)]
+#[clap(
+    version = crate_version!(),
+    author = crate_authors!(", "),
+    global_setting = AppSettings::InferSubcommands,
+    global_setting = AppSettings::PropagateVersion,
+)]
+pub struct Opts {
+    /// Provide a path to the configuration file
+    #[clap(short, long, value_name = "FILE")]
+    pub config: Option<String>,
+    #[clap(subcommand)]
+    pub command: Option<Command>,
+}