Use non-root user in the docker image

It is better to create a user who does not have root rights and to launch duniter with this user

changed milestone to %ğdev currency launch

added P5-sometimesoon label

assigned to @pini-gh

mentioned in commit a58de59d

mentioned in commit 7b4bec46

mentioned in commit 06f9c34f

added S-needreview label

mentioned in commit a3564139

closed with commit b85e3528

mentioned in commit b85e3528

removed S-needreview label