Switchable tokenizer (#776)

* [REFACTORING]Rename whitespace_tokenizer to tag_tokenizer for
registration

Name representing its purpose is preferred.

* Add lindera-tantivy to plume-model's dependencies

* Install lindera-tantivy

* Add SearchTokenizerConfig struct

* Add search tokenizers to config option

* Use CONFIG for tokenizers

* Use enum to hold tokenizer config instead of initializing on config phase

* Use guard instead of duplicate default values

* Use as_deref() instead of guard

* Move SearchTokenizer from plume-models to plume-models::search::tokenizer

* Rename SearchTokenizer to TokenizerKind

* Define SearchTokenierConfig::determine_tokenizer()

* Use determine_tokenizer in SearchTokenizerConfig::init()

* Pass tokenizer config to Searcher methods

* Add LowerCase filter to Lindera tokenizer

* Add test for Lindera tokenizer

* Define SEARCH_LANG env to specify tokenizers set

* Run cargo fmt

* Make Lindera tokenizer optional

* Fix typos

plume-models/src/lib.rs

@@ -320,7 +320,7 @@ mod tests {
     pub fn rockets() -> super::PlumeRocket {
         super::PlumeRocket {
             conn: db_conn::DbConn((*DB_POOL).get().unwrap()),
-            searcher: Arc::new(search::tests::get_searcher()),
+            searcher: Arc::new(search::tests::get_searcher(&CONFIG.search_tokenizers)),
             worker: Arc::new(ScheduledThreadPool::new(2)),
             user: None,
         }