New search engine (#4378)

* New possibility to invoke user queries from a search expression
From the search field: `S:"My query"`.
Can be combined with other filters such as `S:"My query" date:P3d` as long as the user queries do not contain `OR`.
A use-case is to have an RSS filter with a stable address or an external API call with the ability to update the user query.

* Draft of parenthesis logic

* More draft

* Working parenthesis (a OR b) (c OR d)

* Working (A) OR (B)

* Support nested parentheses + unit tests + documentation

* search:MySearch and S:3

1 files changed, 8 insertions, 8 deletions

diff --git a/app/Models/EntryDAOSQLite.php b/app/Models/EntryDAOSQLite.php
index 16d15f899..e4e079959 100644
--- a/app/Models/EntryDAOSQLite.php
+++ b/app/Models/EntryDAOSQLite.php
@@ -2,19 +2,23 @@
 
 class FreshRSS_EntryDAOSQLite extends FreshRSS_EntryDAO {
 
-	public function isCompressed(): bool {
+	public static function isCompressed(): bool {
 		return false;
 	}
 
-	public function hasNativeHex(): bool {
+	public static function hasNativeHex(): bool {
 		return false;
 	}
 
-	public function sqlHexDecode(string $x): string {
+	protected static function sqlConcat($s1, $s2) {
+		return $s1 . '||' . $s2;
+	}
+
+	public static function sqlHexDecode(string $x): string {
 		return $x;
 	}
 
-	public function sqlIgnoreConflict(string $sql): string {
+	public static function sqlIgnoreConflict(string $sql): string {
 		return str_replace('INSERT INTO ', 'INSERT OR IGNORE INTO ', $sql);
 	}
 
@@ -65,10 +69,6 @@ DROP TABLE IF EXISTS `tmp`;
 		return $result;
 	}
 
-	protected function sqlConcat($s1, $s2) {
-		return $s1 . '||' . $s2;
-	}
-
 	protected function updateCacheUnreads($catId = false, $feedId = false) {
 		$sql = 'UPDATE `_feed` '
 		 . 'SET `cache_nbUnreads`=('