fix: be case-insensitive when using bleve for issue search (#11022)

The indexer previously used a `camelcase` filter which could be problamatic for certain queries.
This commit removes the faulty filter for bleve, matching the behaviour of the database "indexer".

closes !10997

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11022
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Shiny Nematoda <snematoda.751k2@aleeas.com>
Co-committed-by: Shiny Nematoda <snematoda.751k2@aleeas.com>

modules/indexer/issues/bleve/bleve.go

@@ -13,7 +13,6 @@ import (
 
 	"github.com/blevesearch/bleve/v2"
 	"github.com/blevesearch/bleve/v2/analysis/analyzer/custom"
-	"github.com/blevesearch/bleve/v2/analysis/token/camelcase"
 	"github.com/blevesearch/bleve/v2/analysis/token/lowercase"
 	"github.com/blevesearch/bleve/v2/analysis/token/unicodenorm"
 	"github.com/blevesearch/bleve/v2/analysis/tokenizer/unicode"
@@ -24,7 +23,7 @@ import (
 const (
 	issueIndexerAnalyzer      = "issueIndexer"
 	issueIndexerDocType       = "issueIndexerDocType"
-	issueIndexerLatestVersion = 5
+	issueIndexerLatestVersion = 6
 )
 
 const unicodeNormalizeName = "unicodeNormalize"
@@ -100,7 +99,7 @@ func generateIssueIndexMapping() (mapping.IndexMapping, error) {
 		"type":          custom.Name,
 		"char_filters":  []string{},
 		"tokenizer":     unicode.Name,
-		"token_filters": []string{unicodeNormalizeName, camelcase.Name, lowercase.Name},
+		"token_filters": []string{unicodeNormalizeName, lowercase.Name},
 	}); err != nil {
 		return nil, err
 	}

modules/indexer/issues/indexer_test.go

@@ -53,6 +53,13 @@ func searchIssueWithKeyword(t *testing.T) {
 			},
 			[]int64{2},
 		},
+		{
+			"ISSUe2", // case-insensitive search
+			&SearchOptions{
+				RepoIDs: []int64{1},
+			},
+			[]int64{2},
+		},
 		{
 			"first",
 			&SearchOptions{