feat: add salary privilege to privilege management system

Add support for the salary privilege in the privilege handler. 
Implement associated logic to process and validate the 
salary privilege in the test cases. Update the data 
structures to include the new privilege and ensure 
correct functionality in the privilege processing flow.

client_test.go

@@ -236,6 +236,18 @@ func TestPrivilegeHandler_IsAllowed_Return_True_If_Privilege_Exists(t *testing.T
 	})
 
 	assert.True(t, result)
+
+	_, _ = handler.Process(&PrivilegeAdded{
+		Email:     "jim@example.org",
+		CompanyID: "abc-123",
+		Privilege: PrivilegeSalary,
+	}, goamqp.Headers{})
+
+	result = handler.IsAllowed("jim@example.org", "abc-123", func(privileges CompanyPrivileges) bool {
+		return privileges.Salary
+	})
+
+	assert.True(t, result)
 }
 
 func TestPrivilegeHandler_Fetch_Error_Response(t *testing.T) {
@@ -289,7 +301,8 @@ func TestPrivilegeHandler_Fetch_Valid(t *testing.T) {
       "time": true,
       "invoicing": true,
       "accounting": false,
-      "supplier": false
+      "supplier": false,
+      "salary": true
     }
   }
 }`
@@ -313,6 +326,7 @@ func TestPrivilegeHandler_Fetch_Valid(t *testing.T) {
 				Invoicing:  true,
 				Accounting: false,
 				Supplier:   false,
+				Salary:     true,
 			},
 		},
 	}