feat: Adds some documenation comments

Sources/SharedModels/Employee.swift

@@ -1,6 +1,9 @@
 import Dependencies
 import Foundation
 
+/// Represents an employee database model.
+///
+/// Employee's are who purchase orders can be generated for.
 public struct Employee: Codable, Equatable, Identifiable, Sendable {
   public var id: UUID
   public var active: Bool
@@ -31,6 +34,8 @@ public struct Employee: Codable, Equatable, Identifiable, Sendable {
 }
 
 public extension Employee {
+  /// Represents the required fields for generating a new employee in the
+  /// database.
   struct Create: Codable, Sendable, Equatable {
     public let firstName: String
     public let lastName: String
@@ -47,6 +52,8 @@ public extension Employee {
     }
   }
 
+  /// Represents the required fields for updating an existing employee in the
+  /// database.
   struct Update: Codable, Sendable, Equatable {
     public let firstName: String?
     public let lastName: String?