Passman on Nextcloud (database PostgreSQL)

Bug report

Not support PostgreSQL

Steps to reproduce

1. When trying to add Passman to Nextcloud can't to add (if have PostgreSQL - on MySql work)

Expected behaviour

I relly love passman and hope passman will add support for PostgreSQL database.

Actual behaviour

Tell us what happens instead

Configuration

Operating system: Debian 9 GNU/Linux

Browser: Waterfox

Extensions that might cause interference:

Passman version:

Operating system: Debian 9 GNU/Linux

Web server: Apache

Database: PostgreSQL

PHP version: 7.0

cloud server: Nextcloud

cloud version: 12.0.4

Cloud log

{"reqId":"es9mToE2Ydvuy0BgdnPI","level":3,"time":"2018-01-19T09:15:31+00:00","remoteAddr":"192.168.4.226","user":"ivan","app":"core","method":"POST","url":"\/index.php\/settings\/ajax\/enableapp.php","message":"An exception occurred while executing 'ALTER TABLE oc_passman_share_request ALTER item_id TYPE BIGINT':\n\nSQLSTATE[42804]: Datatype mismatch: 7 ERROR:  column \"item_id\" cannot be cast automatically to type bigint\nHINT:  You might need to specify \"USING item_id::bigint\".","userAgent":"Mozilla\/5.0 (X11; Linux x86_64; rv:56.0) Gecko\/20100101 Firefox\/56.0.3 Waterfox\/56.0.3","version":"12.0.4.3"}

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Start by reproducing Passman activation through Nextcloud's enableapp.php entry point with PostgreSQL and inspect the logged ALTER TABLE failure on oc_passman_share_request.item_id. Done means Passman can be enabled on PostgreSQL without this datatype-mismatch error; the issue does not name a source file or test to run.