document the clamav max stream setting

.env.example

@@ -209,7 +209,8 @@ COLLABORA_SSL_VERIFICATION=false
 ### Virusscanner Settings ###
 # IMPORTANT: If you enable antivirus, you also MUST configure the START_ADDITIONAL_SERVICES
 # envvar in the OpenCloud Settings above by adding 'antivirus' to the list.
-# The maximum scan size the virus scanner can handle, needs adjustment in the scanner config as well.
+# The maximum scan size the virus scanner can handle, needs adjustment in the scanner config as well:
+# For ClamAV, set CLAMD_CONF_StreamMaxLength in antivirus/clamav.yml to the same or a higher value.
 # Usable common abbreviations: [KB, KiB, MB, MiB, GB, GiB, TB, TiB, PB, PiB, EB, EiB], example: 2GB.
 # Defaults to "100MB"
 #ANTIVIRUS_MAX_SCAN_SIZE=

antivirus/clamav.yml

@@ -14,6 +14,10 @@ services:
       - clamav-socket:/var/run/clamav
   clamav:
     image: clamav/clamav:${CLAMAV_DOCKER_TAG:-latest}
+    environment:
+      # Accepts a number with optional K, M or G suffix. Must be greater or equal to ANTIVIRUS_MAX_SCAN_SIZE above.
+      # K = KiB (1024), M = MiB (1024 * 1024), G = GiB (1024 * 1024 * 1024)
+      CLAMD_CONF_StreamMaxLength: 100M
     networks:
       opencloud-net:
     volumes: