tests/main/system-usernames-hooks: a snap using system-usernames and hooks

tests/main/system-usernames-hooks/task.yaml

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+summary: exercise snap hooks using system-usernames
+
+details: |
+    Exercise a scenario in which a snap that uses system-usernames carries
+    hooks. Make sure that hooks are able to exercise functionality provided by
+    system-usernames.
+
+prepare: |
+    tests.cleanup defer "$TESTSTOOLS"/user-state remove-with-group snap_daemon
+
+execute: |
+    "$TESTSTOOLS"/snaps-state install-local test-snapd-sh
+    test-snapd-sh.sh -c 'setpriv --clear-groups \
+            --reuid snap_daemon \
+            --regid snap_daemon -- \
+            id'
+
+    "$TESTSTOOLS"/snaps-state install-local test-snapd-sh

tests/main/system-usernames-hooks/test-snapd-sh/bin/sh

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+#!/bin/sh
+PS1='$ '
+exec /bin/sh "$@"

tests/main/system-usernames-hooks/test-snapd-sh/meta/hooks/install

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+#!/bin/sh
+
+exec 2>&1
+
+echo "running install hook" >> "$SNAP_COMMON"/hook.log
+
+mkdir "$SNAP_COMMON"/data
+touch "$SNAP_COMMON"/data/foo
+
+chown -R snap_daemon "$SNAP_COMMON"/data
+chgrp -R root "$SNAP_COMMON"/data

tests/main/system-usernames-hooks/test-snapd-sh/meta/hooks/post-refresh

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+#!/bin/sh
+
+exec 2>&1
+
+echo "running post-refresh hook" >> "$SNAP_COMMON"/hook.log
+
+setpriv \
+    --clear-groups \
+    --reuid snap_daemon \
+    --regid snap_daemon -- \
+            /bin/sh -c "echo 'post refresh' >> $SNAP_COMMON/data/foo"

tests/main/system-usernames-hooks/test-snapd-sh/meta/snap.yaml

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+name: test-snapd-sh
+summary: Minimal snap for testing
+version: 1.0
+base: core24
+
+apps:
+    sh:
+        command: bin/sh
+
+system-usernames:
+  snap_daemon: shared