FIX: Allow for custom admin url #1159

Job	Run time
CI / Context	1s
CI / Generate matrix	12s
CI / Check governance	0s
CI / 8.1 prf-low mysql57 phpunit all	2m 53s
CI / 8.2 mariadb phpunit all	2m 48s
CI / 8.3 mysql80 phpunit all	3m 3s
CI / 8.3 mysql84 phpunit all	3m 25s
CI / 8.1 mysql57 phplinting	2m 23s
CI / 8.1 mysql57 endtoend root job1	8m 29s
CI / 8.3 mysql80 endtoend root job1	8m 51s
CI / 8.1 mysql57 endtoend root job2	8m 3s
CI / 8.3 mysql80 endtoend root job2	8m 55s
CI / 8.1 mysql57 endtoend root job3	9m 40s
CI / 8.3 mysql80 endtoend root job3	16m 26s
CI / 8.1 mysql57 endtoend root job4	9m 14s
CI / 8.3 mysql80 endtoend root job4	9m 22s
CI / 8.1 mysql57 endtoend root job5	6m 27s
CI / 8.3 mysql80 endtoend root job5	6m 24s
CI / 8.1 mysql57 endtoend root job6	8m 21s
CI / 8.3 mysql80 endtoend root job6	8m 37s
CI / 8.1 mysql57 endtoend root job7	11m 32s
CI / 8.3 mysql80 endtoend root job7	11m 36s
CI / 8.1 mysql57 js	4m 55s
CI / 8.1 mysql57 doclinting	2m 34s
CI / Dispatch tag patch release	0s
	2h 34m 11s

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