fix: resolve clippy warnings for argument count and FromStr trait

- Allow too_many_arguments for AppState::new since 8 repos are needed
- Implement FromStr trait for GearCategory instead of custom from_str
  method to follow Rust conventions
- Update callers to use map_err for Result handling

src/application/routes/gear.rs

@@ -1,3 +1,5 @@
+use std::str::FromStr;
+
 use axum::Json;
 use axum::extract::{Path, Query, State};
 use axum::http::{HeaderMap, StatusCode};
@@ -140,7 +142,7 @@ pub(crate) async fn list_gear(
     let filter = match params.category {
         Some(ref cat_str) => {
             let category = GearCategory::from_str(cat_str)
-                .ok_or_else(|| AppError::validation("invalid category"))?;
+                .map_err(|_| AppError::validation("invalid category"))?;
             GearFilter::for_category(category)
         }
         None => GearFilter::all(),
@@ -206,7 +208,7 @@ pub(crate) struct NewGearSubmission {
 impl NewGearSubmission {
     fn into_new_gear(self) -> Result<NewGear, AppError> {
         let category = GearCategory::from_str(&self.category)
-            .ok_or_else(|| AppError::validation("invalid category"))?;
+            .map_err(|_| AppError::validation("invalid category"))?;
 
         if self.make.trim().is_empty() {
             return Err(AppError::validation("make cannot be empty"));

src/application/server.rs

@@ -44,6 +44,7 @@ pub struct AppState {
 }
 
 impl AppState {
+    #[allow(clippy::too_many_arguments)]
     pub fn new(
         roaster_repo: Arc<dyn RoasterRepository>,
         roast_repo: Arc<dyn RoastRepository>,

src/domain/gear.rs

@@ -1,3 +1,5 @@
+use std::str::FromStr;
+
 use chrono::{DateTime, Utc};
 use serde::{Deserialize, Serialize};
 
@@ -19,14 +21,6 @@ impl GearCategory {
         }
     }
 
-    pub fn from_str(s: &str) -> Option<Self> {
-        match s.to_lowercase().as_str() {
-            "grinder" => Some(GearCategory::Grinder),
-            "brewer" => Some(GearCategory::Brewer),
-            _ => None,
-        }
-    }
-
     pub fn display_label(&self) -> &'static str {
         match self {
             GearCategory::Grinder => "Grinder",
@@ -35,6 +29,18 @@ impl GearCategory {
     }
 }
 
+impl FromStr for GearCategory {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.to_lowercase().as_str() {
+            "grinder" => Ok(GearCategory::Grinder),
+            "brewer" => Ok(GearCategory::Brewer),
+            _ => Err(()),
+        }
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Gear {
     pub id: GearId,

src/infrastructure/repositories/gear.rs

@@ -1,3 +1,5 @@
+use std::str::FromStr;
+
 use async_trait::async_trait;
 use chrono::{DateTime, Utc};
 use sqlx::{QueryBuilder, query_as};
@@ -35,7 +37,7 @@ impl SqlGearRepository {
     }
 
     fn to_domain(record: GearRecord) -> Result<Gear, RepositoryError> {
-        let category = GearCategory::from_str(&record.category).ok_or_else(|| {
+        let category = GearCategory::from_str(&record.category).map_err(|_| {
             RepositoryError::unexpected(format!("invalid category: {}", record.category))
         })?;