hotfix: read env variables for config params with _ in their names

ref: https://github.com/mehcode/config-rs/issues/391

src/settings.rs

@@ -19,11 +19,15 @@ use std::path::Path;
 
 use config::{Config, ConfigError, Environment, File};
 use derive_more::Display;
+use log::info;
 use log::warn;
 use serde::Deserialize;
 use serde::Serialize;
 use url::Url;
 
+const PREFIX: &str = "LPCONDUCTOR";
+const SEPARATOR: &str = "__";
+
 #[derive(Debug, Clone, Deserialize)]
 pub struct Server {
     pub port: u32,
@@ -72,10 +76,11 @@ impl Settings {
         } else if Path::new(ETC).exists() {
             s.merge(File::with_name(ETC))?;
         } else {
-            log::warn!("configuration file not found");
+            warn!("configuration file not found");
         }
 
-        s.merge(Environment::with_prefix("LPCONDUCTOR").separator("_"))?;
+        s.merge(Environment::with_prefix(PREFIX).separator(SEPARATOR))?;
+        set_separator_field(&mut s);
 
         check_url(&s);
 
@@ -95,6 +100,31 @@ impl Settings {
     }
 }
 
+#[cfg(not(tarpaulin_include))]
+fn set_separator_field(s: &mut Config) {
+    // ref: https://github.com/mehcode/config-rs/issues/391
+
+    fn from_env(s: &mut Config, env_name: &str, config_name: &str) {
+        if let Ok(val) = env::var(env_name) {
+            info!("Overriding {config_name} with data from env var {env_name}");
+            s.set(config_name, val).unwrap_or_else(|_| panic!(
+                "Couldn't set {config_name}  from env var {env_name}"
+            ));
+        }
+    }
+    from_env(s, &format!("{PREFIX}{SEPARATOR}SOURCE_CODE"), "source_code");
+    from_env(
+        s,
+        &format!("{PREFIX}{SEPARATOR}SERVER{SEPARATOR}URL_PREFIX"),
+        "server.url_prefix",
+    );
+    from_env(
+        s,
+        &format!("{PREFIX}{SEPARATOR}SERVER{SEPARATOR}PROXY_HAS_TLS"),
+        "server.proxy_has_tls",
+    );
+}
+
 #[cfg(not(tarpaulin_include))]
 fn check_url(s: &Config) {
     let url = s