Implement the in-process structured entry editor

Closes #21

crates/storage/src/generate.rs

@@ -46,6 +46,31 @@ impl GeneratorConfig {
     pub fn character_set(&self) -> &[char] {
         &self.character_set
     }
+
+    /// Generate a zeroizing password for an in-process structured editor
+    /// without mutating a repository.
+    pub fn generate_secret(
+        &self,
+        length: Option<NonZeroUsize>,
+        no_symbols: bool,
+    ) -> Result<SecretBytes, GenerateError> {
+        self.generate_secret_with_rng(length, no_symbols, &mut OsRng)
+    }
+
+    fn generate_secret_with_rng<R: RngCore + CryptoRng>(
+        &self,
+        length: Option<NonZeroUsize>,
+        no_symbols: bool,
+        rng: &mut R,
+    ) -> Result<SecretBytes, GenerateError> {
+        let length = validate_length(length.unwrap_or(self.default_length).get())?;
+        let characters = if no_symbols {
+            &self.alphanumeric_set
+        } else {
+            &self.character_set
+        };
+        generate_password(rng, length, characters)
+    }
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -126,14 +151,9 @@ impl<'a> PasswordGenerator<'a> {
         if request.force && request.in_place {
             return Err(GenerateError::IncompatibleFlags);
         }
-        let length = request.length.unwrap_or(self.config.default_length);
-        let length = validate_length(length.get())?;
-        let characters = if request.no_symbols {
-            &self.config.alphanumeric_set
-        } else {
-            &self.config.character_set
-        };
-        let password = generate_password(rng, length, characters)?;
+        let password =
+            self.config
+                .generate_secret_with_rng(request.length, request.no_symbols, rng)?;
         let path = EntryPath::parse(&request.entry)?;
         let contents = if request.in_place {
             let ciphertext = self.repository.read_entry(&path)?;