Alpine container for webhook can fail on update

[glazychev-art]

Expected Behavior

Postgresql should be correctly installed

Current Behavior

Postgresql is not installed on alpine, so TestWebhook failed

Failure Information (for bugs)

Sometimes apk update can return the next errors:

ERROR: http://dl-cdn.alpinelinux.org/alpine/v3.13/main: temporary error (try again later)
ERROR: http://dl-cdn.alpinelinux.org/alpine/v3.13/community: temporary error (try again later)

Proposal

Use postgres container as a client instead of alpine