fix(open-xchange): Optimize Dovecot Pro full-text search caches; review migrations.md for required upgrade steps

helmfile/apps/open-xchange/values-dovecot-enterprise.yaml.gotmpl

@@ -37,11 +37,14 @@ dovecot:
       value: {{ .Values.secrets.dovecot.sharedMailboxesMasterPassword | quote }}
   objectStorage:
     bucket: {{ .Values.objectstores.dovecot.bucket | quote }}
+    cacheTmpfs: {{ if .Values.technical.dovecot.objectStorage.cacheTmpfs }}true{{ else }}false{{ end }}
     encryption:
       privateKey:
         value: {{ requiredEnv "DOVECOT_CRYPT_PRIVATE_KEY" | quote }}
       publicKey:
         value: {{ requiredEnv "DOVECOT_CRYPT_PUBLIC_KEY" | quote }}
+    fsCacheSize: {{ .Values.technical.dovecot.objectStorage.fsCacheSize | quote }}
+    ftsCacheSize: {{ .Values.technical.dovecot.objectStorage.ftsCacheSize | quote }}
     fqdn: {{ .Values.objectstores.dovecot.endpoint | default (printf "%s.%s" .Values.global.hosts.minioApi .Values.global.domain) | quote }}
     username: {{ .Values.objectstores.dovecot.username | quote }}
     password:

helmfile/environments/default/persistence.yaml.gotmpl

@@ -16,6 +16,8 @@ persistence:
       size: "1Gi"
       storageClassName: ~
     dovecot:
+      # With Dovecot CE this is used for the mail storage.
+      # Dovecot Pro (EE) uses this storage for the metacache,
       size: "1Gi"
       storageClassName: ~
     mariadb:

helmfile/environments/default/technical.yaml.gotmpl

@@ -8,6 +8,18 @@ technical:
     # Defines the value for the start parameter `-o:num_prespawn_children`
     numPrespawnChildren: 4
 
+  # Dovecot EE related settings
+  dovecot:
+    objectStorage:
+      # Size of objectstore fs cache
+      fsCacheSize: "2G"
+      # Size of fts cache
+      ftsCacheSize: "2G"
+      # Wether fs and fts cache should reside in RAM (tmpfs) or not
+      # If this value is true, the cache sizes of the fs cache + fts cache
+      # must be considered additionally to Dovecot's memory footprint.
+      cacheTmpfs: false
+
   # Nubus related settings
   nubus:
     # Nubus provisioning framework that is being used to actively provision data internally within