feat(backup_manager): add new exercise subject for quest 8 scripting piscine

subjects/devops/backup_manager/README.md

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+## Backup manager
+
+### Instructions
+
+You will create two scripts that will manage and perform scheduled backups.
+
+#### First script: backup_manager.py
+
+The script `backup_manager.py` will orchestrate the backup service and if necessary update the file `backup_schedules.txt`. In order to do so it will accept the following command-line arguments:
+
+- `start`: run `backup_service.py` in the background.
+- `stop`: stop the process `backup_service.py`.
+- `create [schedule]`: add a new backup schedule in `backup_schedules.txt`.
+- `delete [index]`: delete the backup schedule at line `index` (starting by 0) in `backup_schedules.txt`.
+- `list`: print the scheduled backups in `backup_schedules.txt`, adding an index before each schedule.
+- `backups`: list the backups files in `./backups`.
+
+#### Second script: backup_service.py
+
+The script `backup_service.py` will check the schedules in `backup_schedules.txt` and perform the daily backups at the proper time.
+
+- The service will run in an infinite loop.
+- On every cycle of the loop the service will check the schedules.
+- The service will perform the backup if the current time (hour and minute) matches the time of the schedule.
+- The format of the schedules is `path_to_save;time(hh:mm);backup_name`.
+- The backups will be saved in `./backups`.
+- The backups will be a compressed file (`.tar`) for the `path_to_save` directory.
+
+> At the end of each loop it would be wise to make the service sleep for about 45 seconds to save processor cycles.
+
+### Logs and error handling
+
+Both scripts will have to use `try` and `except` to handle errors.
+All actions and errors should be logged into a specific file in the `./log` directory.
+
+- `backup_manager.py` will log into `./logs/backup_manager.log`.
+- `backup_service.py` will log into `./logs/backup_service.log`.
+
+You can choose to phrase your logs as you prefer, however it would be smart to start with a timestamp and try to be as specific as you can.
+
+### Usage
+
+Here is a little script to show how the backup system should work:
+
+```bash
+echo "--> Create 3 new schedules"
+python3 ./backup_manager.py create "test;16:07;backup_test"
+python3 ./backup_manager.py create "test1;16:07;personal_data"
+python3 ./backup_manager.py create "test2;16:07;office_docs"
+echo "--> Try to add a malformed schedule"
+python3 ./backup_manager.py create "test;"
+echo "--> Instruction list"
+python3 ./backup_manager.py list
+
+python3 ./backup_manager.py start
+python3 ./backup_manager.py stop
+
+echo "--> Instruction backups"
+python3 ./backup_manager.py backups
+
+echo "--> Content of the directory"
+ls
+echo "--> cat on ./logs/backup_manager.log"
+cat ./logs/backup_manager.log
+echo "--> cat on ./logs/backup_service.log"
+cat ./logs/backup_service.log
+echo "--> Content of ./backups"
+ls ./backups
+```
+
+The output of this script should be similar to the following:
+
+```console
+--> Create 3 new schedules
+--> Try to add a malformed schedule
+--> Instruction list
+0: test;16:07;backup_test
+1: test1;16:07;personal_data
+2: test2;16:07;office_docs
+--> Instruction backups
+personal_data.tar
+office_docs.tar
+backup_test.tar
+--> Content of the directory
+backup_manager.py  backups  backup_schedules.txt  backup_service.py  logs
+--> cat on ./logs/backup_manager.log
+[08/02/2023 16:07] New schedule added: test;16:07;backup_test
+[08/02/2023 16:07] New schedule added: test1;16:07;personal_data
+[08/02/2023 16:07] New schedule added: test2;16:07;office_docs
+[08/02/2023 16:07] Error: malformed schedule: test;
+[08/02/2023 16:07] Show schedules list
+[08/02/2023 16:07] backup_service started
+[08/02/2023 16:07] backup_service stopped
+[08/02/2023 16:07] Show backups list
+--> cat on ./logs/backup_service.log
+[08/02/2023 16:07] Backup done for test in backups/backup_test.tar
+[08/02/2023 16:07] Backup done for test1 in backups/personal_data.tar
+[08/02/2023 16:07] Backup done for test2 in backups/office_docs.tar
+--> Content of ./backups
+backup_test.tar  office_docs.tar  personal_data.tar
+```
+
+### Hints
+
+- To run a script from another python script you could use `subprocess.Popen` with the flag `start_new_session=True`.
+- To kill a process you should find its process id and call `os.kill`.
+- Play with the command `ps -A -f`, it will show a list of all active processes with the arguments attached to them and their process ids.
+- The standard library `tarfile` is very useful when trying to work with archives.
+- This starts to be quite a big project, try to be as modular as you can by creating single-task functions, this will save you a lot of time.
+
+> There is many ways to run tasks in background and to perform actions on a specific time, the implementation proposed in this exercise is good for learning but should not be your preferred choice for production environments.
+
+### References
+
+- [Error handling in Python](https://docs.python.org/3.10/tutorial/errors.html)
+- [Spawn a subprocess in Python](https://docs.python.org/3.10/library/subprocess.html)