Use max-mails setting with higher priority

The `mail-chunk-size` is set to its configured value or `max-mails`
whichever is lower.

modules/joex/src/main/resources/reference.conf

@@ -106,14 +106,18 @@ docspell.joex {
       max-folders = 50
 
       # How many mails (headers only) to retrieve in one chunk.
-      mail-chunk-size = 100
+      #
+      # If this is greater than `max-mails' it is set automatically to
+      # the value of `max-mails'.
+      mail-chunk-size = 50
 
       # A limit on how many mails to process in one job run. This is
-      # only to avoid resource allocation to one user/collective.
+      # meant to avoid too heavy resource allocation to one
+      # user/collective.
       #
       # If more than this number of mails is encountered, a warning is
       # logged.
-      max-mails = 1000
+      max-mails = 500
     }
   }
 

modules/joex/src/main/scala/docspell/joex/Config.scala

@@ -29,6 +29,9 @@ case class Config(
 object Config {
   case class Bind(address: String, port: Int)
 
-  case class ScanMailbox(maxFolders: Int, mailChunkSize: Int, maxMails: Int)
+  case class ScanMailbox(maxFolders: Int, mailChunkSize: Int, maxMails: Int) {
+    def mailBatchSize: Int =
+      math.min(mailChunkSize, maxMails)
+  }
   case class UserTasks(scanMailbox: ScanMailbox)
 }

modules/joex/src/main/scala/docspell/joex/scanmailbox/ScanMailboxTask.scala

@@ -164,11 +164,11 @@ object ScanMailboxTask {
       for {
         _ <- Kleisli.liftF(
           ctx.logger.debug(
-            s"Searching next ${cfg.mailChunkSize} mails in ${folder.name}."
+            s"Searching next ${cfg.mailBatchSize} mails in ${folder.name}."
           )
         )
         query <- Kleisli.liftF(q)
-        mails <- a.search(folder, cfg.mailChunkSize)(query)
+        mails <- a.search(folder, cfg.mailBatchSize)(query)
         _ <- Kleisli.liftF(
           ctx.logger.debug(
             s"Found ${mails.count} mails in folder. Reading first ${mails.mails.size}"