Refactoring loading of config file

- let `HuskConfig::load` return a `Result` instead of an `Option`.
- added comments

src/types/errors.rs

@@ -8,6 +8,10 @@ use thiserror::Error;
 
 #[derive(Error, Debug)]
 pub enum HuskError {
+    #[error("Cannot open config file: {0}")]
+    ConfigFileOpenError(String),
+    #[error("Error while parsing config file: {0}")]
+    ConfigFileParseError(String),
     #[error("Cannot find local trust root")]
     NoLocalTrustRoot,
     #[error("Cannot access cert store")]

src/types/introducer.rs

@@ -19,7 +19,7 @@ impl Introducer {
     pub fn can_introduce(&self, email: &str) -> bool {
         if let Some(regexset) = self.certification.regular_expressions() {
             if regexset.matches_everything() {
-                // return false, because unlimited certifications are 
+                // return false, because unlimited certifications are
                 // ignored.
                 false
             } else {

src/types/mail_context.rs

@@ -12,8 +12,11 @@ use crate::types::recipient::Recipient;
 
 #[derive(PartialEq)]
 pub enum ProtectionPossibility {
+    // no recipient has a cert
     NoProtection,
+    // some recipients have a cert (but not all)
     Partial,
+    // all recipients have a cert
     Full
 }
 
@@ -82,7 +85,8 @@ impl From<&MailContext<'_>> for ProtectionPossibility {
             (true, false) => ProtectionPossibility::Full,
             (true, true) => ProtectionPossibility::Partial,
             (false, true) => ProtectionPossibility::NoProtection,
-            (false, false) => ProtectionPossibility::NoProtection, // this should not occure
+            // (false, false) occurs if there are no recipients
+            (false, false) => ProtectionPossibility::NoProtection,
         }
     }
 }

src/types/recipient.rs

@@ -37,10 +37,14 @@ impl TryFrom<CString> for Recipient<'_> {
 }
 
 impl Recipient<'_> {
+    /// check if this Recipient can encrypt.
+    // XXX: currently this check is naive
     pub fn can_encrypt(&self) -> bool {
         if self.certs.len() == 0 { 
             return false;
         }
+
+        // XXX: add check to see if a cert has encryption capable subkeys
         true
     }
 }