prohibit multiple employees on the same run. adjust column order

Author: skyqrose

docs/spec/examples.md

@@ -202,19 +202,19 @@ weekend,104,1,work,trip4,station,09:00:00,station,17:00:00
 **[`employee_run_dates.txt`](/docs/spec.md#employee_run_datestxt)**
 
 ```csv
-date,employee_id,service_id,run_id
-20240701,A,weekday,101
-20240701,B,weekday,102
-20240702,A,weekday,101
-20240702,B,weekday,102
-20240703,A,weekday,101
-20240703,B,weekday,102
-20240704,C,weekday,101
-20240704,D,weekday,102
-20240705,C,weekday,101
-20240705,D,weekday,102
-20240706,C,weekend,103
-20240706,D,weekend,104
-20240707,A,weekend,103
-20240707,B,weekend,104
+date,service_id,run_id,employee_id
+20240701,weekday,101,A
+20240701,weekday,102,B
+20240702,weekday,101,A
+20240702,weekday,102,B
+20240703,weekday,101,A
+20240703,weekday,102,B
+20240704,weekday,101,C
+20240704,weekday,102,D
+20240705,weekday,101,C
+20240705,weekday,102,D
+20240706,weekend,103,C
+20240706,weekend,104,D
+20240707,weekend,103,A
+20240707,weekend,104,B
 ```

docs/spec/index.md

@@ -151,13 +151,13 @@ Run IDs may be non-unique. E.g. E.g. there may be a "Run 100" on both Weekday an
 
 Describes which employees are scheduled to which runs on which dates.
 
-This file should represent the schedule after holidays, vacation, and other scheduled exceptions have been applied.
+This file should represent the schedule after holidays, vacations, and other scheduled exceptions have been applied.
 
-Primary Key: `*`
+Primary Key: (`date`, `service_id`, `run_id`)
 
 | **Field Name** | **Type** | **Required** | **Description** |
 | --- | --- | --- | --- |
 | `date` | Date | Required | Service date. |
-| `employee_id` | ID | Required | References an agency's external systems. Employee IDs are not used elsewhere in TODS. |
 | `service_id` | ID referencing `run_events.txt` | Required | Part of the Run ID, which is refered to as `(service_id, run_id)`. See [Run ID Uniqueness](#run-id-uniqueness). |
 | `run_id` | ID referencing `run_events.txt` | Required | The run that's added to this employee's schedule. |
+| `employee_id` | ID | Required | References an agency's external systems. Employee IDs are not used elsewhere in TODS. |