dovecot: replace solr fts with flatcurve (xapian) (#5680)

* fts-flatcurve: inital implementation

* fts: removed solr from compose.yml

* flatcurve: added heap and proc logic to dovecot

* added logic for update.sh & generate for Flatcurve

* delete old iteration of fts-flatcurve.conf

* updated default fts.conf

* updated .gitignore to exclude fts.conf for further git updates

* Remove autogeneration of fts.conf (disable override)

* cleanup all left solr stuff

* renamed SKIP_FLATCURVE to SKIP_FTS

* cleanup leftovers solr in lang files

* moved lazy_expunge plugin only to mail_plugins

* added fts timeout value

* compose: remove dev image of dovecot

* updated japanese translation

data/conf/dovecot/conf.d/fts.conf

@@ -0,0 +1,35 @@
+# mailcow FTS Flatcurve Settings, change them as you like.
+plugin {
+    fts_autoindex = yes
+    fts_autoindex_exclude = \Junk
+    fts_autoindex_exclude2 = \Trash
+    fts = flatcurve
+
+    # Maximum term length can be set via the 'maxlen' argument (maxlen is
+    # specified in bytes, not number of UTF-8 characters)
+    fts_tokenizer_email_address = maxlen=100
+    fts_tokenizer_generic = algorithm=simple maxlen=30
+
+    # These are not flatcurve settings, but required for Dovecot FTS. See
+    # Dovecot FTS Configuration link above for further information.
+    fts_languages = en es de
+    fts_tokenizers = generic email-address
+
+    # OPTIONAL: Recommended default FTS core configuration
+    fts_filters = normalizer-icu snowball stopwords
+    fts_filters_en = lowercase snowball english-possessive stopwords
+
+    fts_index_timeout = 300
+}
+
+### THIS PART WILL BE CHANGED BY MODIFYING mailcow.conf AUTOMATICALLY DURING RUNTIME! ###
+
+service indexer-worker {
+  # Max amount of simultaniously running indexer jobs.
+  process_limit=5
+
+  # Max amount of RAM used by EACH indexer process.
+  vsz_limit=128 MB
+}
+
+### THIS PART WILL BE CHANGED BY MODIFYING mailcow.conf AUTOMATICALLY DURING RUNTIME! ###