feat: Begins breaking out database interfaces and api controllers into seperate items.

Sources/App/Controllers/ApiController.swift

@@ -1,6 +1,7 @@
 import Fluent
 import Vapor
 
+// TODO: Use DB controllers.
 struct ApiController: RouteCollection {
   func boot(routes: RoutesBuilder) throws {
     let api = routes.grouped("api", "v1")
@@ -29,6 +30,9 @@ struct ApiController: RouteCollection {
 
     purchaseOrders.get(use: purchaseOrdersIndex(req:))
     purchaseOrders.post(use: createPurchaseOrder(req:))
+    purchaseOrders.group(":purchaseOrderID") {
+      $0.get(use: getPurchaseOrder(req:))
+    }
 
     users.get(use: usersIndex(req:))
     api.post("users", use: createUser(req:))
@@ -102,8 +106,6 @@ struct ApiController: RouteCollection {
 
   // MARK: - PurchaseOrders
 
-  // TODO: Add fetch by id.
-
   // TODO: Add pagination and filters.
   @Sendable
   func purchaseOrdersIndex(req: Request) async throws -> [PurchaseOrder.DTO] {
@@ -118,6 +120,27 @@ struct ApiController: RouteCollection {
       .map { $0.toDTO() }
   }
 
+  @Sendable
+  func getPurchaseOrder(req: Request) async throws -> PurchaseOrder.DTO {
+    guard let id = req.parameters.get("purchaseOrderID", as: Int.self) else {
+      throw Abort(.badRequest)
+    }
+
+    guard let purchaseOrder = try await PurchaseOrder.query(on: req.db)
+      .filter(\.$id == id)
+      .with(\.$createdBy)
+      .with(\.$createdFor)
+      .with(\.$vendorBranch, {
+        $0.with(\.$vendor)
+      })
+      .first()
+    else {
+      throw Abort(.notFound)
+    }
+
+    return purchaseOrder.toDTO()
+  }
+
   @Sendable
   func createPurchaseOrder(req: Request) async throws -> PurchaseOrder.DTO {
     try PurchaseOrder.Create.validate(content: req)
@@ -287,11 +310,3 @@ struct ApiController: RouteCollection {
     return branch.toDTO()
   }
 }
-
-struct VendorsIndexQuery: Content {
-  let branches: Bool?
-}
-
-struct EmployeesIndexQuery: Content {
-  let active: Bool?
-}