Bump alpine version

pica-mattermost/Dockerfile

-FROM alpine:3.10
+FROM alpine:3.11
 
 # Some ENV variables
 ENV PATH="/mattermost/bin:${PATH}"

pica-mattermost/entrypoint.sh

 #!/bin/sh
 
+# Function to generate a random salt
+generate_salt() {
+  tr -dc 'a-zA-Z0-9' < /dev/urandom | fold -w 48 | head -n 1
+}
+
 # Read environment variables or set default values
 DB_HOST=${DB_HOST:-db}
 DB_PORT_NUMBER=${DB_PORT_NUMBER:-5432}