various: reuse HTTP client; eliminate intermediate string allocations; add tests

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I18b89e1aae78a400a89c9d89423ce1da6a6a6964

crates/common/src/models.rs

@@ -292,8 +292,6 @@ pub struct RemoteBuilder {
   pub created_at:         DateTime<Utc>,
 }
 
-// --- User Management ---
-
 /// User account for authentication and personalization
 #[derive(Debug, Clone, Serialize, Deserialize, FromRow)]
 pub struct User {
@@ -352,7 +350,7 @@ pub struct UserSession {
   pub last_used_at:       Option<DateTime<Utc>>,
 }
 
-// --- Pagination ---
+// Pagination
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct PaginationParams {
@@ -389,7 +387,7 @@ pub struct PaginatedResponse<T> {
   pub offset: i64,
 }
 
-// --- DTO structs for creation and updates ---
+// DTO structs for creation and updates
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct CreateProject {
@@ -537,7 +535,7 @@ pub struct SystemStatus {
   pub channels_count:    i64,
 }
 
-// --- User DTOs ---
+// User DTOs
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct CreateUser {