Congregation delete fails if any user has a congregation restriction

[jefft]

A small bug we've hit in 2.28.1: a congregation cannot be deleted if any user is restricted to it.

To replicate:

1. Go to Admin -> Congregations and add a new congregation:

2. Under Admin -> User Accounts, pick any user and Edit. In the 'Restrictions' section tick the newly created congregation:

3. Back in Admin -> Congregations, click 'Delete' on the new congregation.
   

The user now sees " An error occurred. Please contact your system administrator for help. " and a stacktrace is generated:

SQLSTATE[23000]: Integrity constraint violation: 1451 Cannot delete or update a parent row: a foreign key constraint fails (`jethro`.`account_congregation_restriction`, CONSTRAINT `account_group_restriction_congregationid` FOREIGN KEY (`congregationid`) REFERENCES `congregation` (`id`))
Line 440 of /srv/www/coastec.net.au/jethro/2.28.1/include/db_object.class.php

USER:       536
REFERER:    https://jethro.coastec.net.au/?view=admin__congregations
USER_AGENT: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:79.0) Gecko/20100101 Firefox/79.0

REQUEST:
Array
(
    [view] => admin__congregations
    [action] => delete
    [congregationid] => 16
)


BACKTRACE:
Array
(
    [0] => Array
        (
            [file] => /srv/www/coastec.net.au/jethro/2.28.1/include/db_object.class.php
            [line] => 440
            [function] => query
            [class] => PDO
            [type] => ->
            [args] => Array
                (
                    [0] => DELETE FROM congregation WHERE id='16'
                )

        )

    [1] => Array
        (
            [file] => /srv/www/coastec.net.au/jethro/2.28.1/views/view_10_admin__1_congregations.class.php
            [line] => 23
            [function] => delete
            [class] => db_object
            [type] => ->
            [args] => Array
                (
                )

        )

    [2] => Array
        (
            [file] => /srv/www/coastec.net.au/jethro/2.28.1/include/system_controller.class.php
            [line] => 130
            [function] => processView
            [class] => View_Admin__Congregations
            [type] => ->
            [args] => Array
                (
                )

        )

    [3] => Array
        (
            [file] => /srv/www/coastec.net.au/jethro/2.28.1/index.php
            [line] => 58
            [function] => run
            [class] => System_Controller
            [type] => ->
            [args] => Array
                (
                )

        )

)

[jefft]

The workaround is to note the ID of the congregation you're trying to delete, as shown in the stacktrace:

                    [0] => DELETE FROM congregation WHERE id='16'

and manually delete the restrictions:

MariaDB [jethro]> delete from account_congregation_restriction where congregationid=16;
Query OK, 1 rows affected (0.01 sec)

[tbar0970]

Thanks for the report.
Jethro needs to handle this scenario more gracefully.
But cascade-deleting the account restrictions wouldn't be the way to go. An account with no congregation restrictions remaining has access to every congregation - which would not have been the original intention!
Jethro should instead block the delete and explain why. The user can then adjust account restrictions as necessary before deleting the congregation.