Variable mapping replaces non-ascii characters with '?' in string values

[lenaschoenburg]

Describe the bug

When using a simple variable mapping, non-ascii characters (eg. umlaute such as "ü") are replaced with '?'.

To Reproduce

1. Deploy this model: non-ascii-mapping.bpmn
2. Start a process instance with a source variable: {"source": "äüö"}
3. After the mapping the variables will be {"source": "äüö", "target": "???"}

This is not reproducible with 1.2.9.

Expected behavior
Non-ascii characters are supported.

[Zelldon]

Based on the information here https://stackoverflow.com/a/23932541/2165134 we were able to track the bug down to encoding issues on the local env.

With 1.2.9 we have set the encoding:

root@88ceae3dd2cb:/usr/local/zeebe# locale
LANG=C.UTF-8
LANGUAGE=
LC_CTYPE="C.UTF-8"
LC_NUMERIC="C.UTF-8"
LC_TIME="C.UTF-8"
LC_COLLATE="C.UTF-8"
LC_MONETARY="C.UTF-8"
LC_MESSAGES="C.UTF-8"
LC_PAPER="C.UTF-8"
LC_NAME="C.UTF-8"
LC_ADDRESS="C.UTF-8"
LC_TELEPHONE="C.UTF-8"
LC_MEASUREMENT="C.UTF-8"
LC_IDENTIFICATION="C.UTF-8"
LC_ALL=

With 1.3.0 not (reproduced also by @oleschoenburg )
1.3.0:

root@65cdf6b25ed0:/usr/local/zeebe# locale
LANG=
LANGUAGE=
LC_CTYPE="POSIX"
LC_NUMERIC="POSIX"
LC_TIME="POSIX"
LC_COLLATE="POSIX"
LC_MONETARY="POSIX"
LC_MESSAGES="POSIX"
LC_PAPER="POSIX"
LC_NAME="POSIX"
LC_ADDRESS="POSIX"
LC_TELEPHONE="POSIX"
LC_MEASUREMENT="POSIX"
LC_IDENTIFICATION="POSIX"
LC_ALL=

We have switched to a new docker image with 1.3.0 (eclipse java image based on ubuntu)