Add isUnicode parameter to StringLiteralQueryType function

Author: gilsonjoanelo

src/FirebirdSql.EntityFrameworkCore.Firebird/Query/Internal/FbQuerySqlGenerator.cs

@@ -191,8 +191,9 @@ protected override Expression VisitSqlConstant(SqlConstantExpression sqlConstant
 		base.VisitSqlConstant(sqlConstantExpression);
 		if (shouldExplicitStringLiteralTypes)
 		{
+			var isUnicode = FbTypeMappingSource.IsUnicode(sqlConstantExpression.TypeMapping);	
 			Sql.Append(" AS ");
-			Sql.Append(((IFbSqlGenerationHelper)Dependencies.SqlGenerationHelper).StringLiteralQueryType(sqlConstantExpression.Value as string));
+			Sql.Append(((IFbSqlGenerationHelper)Dependencies.SqlGenerationHelper).StringLiteralQueryType(sqlConstantExpression.Value as string, isUnicode));
 			Sql.Append(")");
 		}
 		return sqlConstantExpression;

src/FirebirdSql.EntityFrameworkCore.Firebird/Storage/Internal/FbSqlGenerationHelper.cs

@@ -27,11 +27,15 @@ public FbSqlGenerationHelper(RelationalSqlGenerationHelperDependencies dependenc
 		: base(dependencies)
 	{ }
 
-	public virtual string StringLiteralQueryType(string s)
+	public virtual string StringLiteralQueryType(string s, bool isUnicode = true)
 	{
 		var length = MinimumStringQueryTypeLength(s);
 		EnsureStringLiteralQueryTypeLength(length);
-		return $"VARCHAR({length}) CHARACTER SET UTF8";
+		if(isUnicode)
+		{
+			return $"VARCHAR({length}) CHARACTER SET UTF8";
+		}
+		return $"VARCHAR({length})";
 	}
 
 	public virtual string StringParameterQueryType(bool isUnicode)

src/FirebirdSql.EntityFrameworkCore.Firebird/Storage/Internal/IFbSqlGenerationHelper.cs

@@ -22,7 +22,7 @@ namespace FirebirdSql.EntityFrameworkCore.Firebird.Storage.Internal;
 
 public interface IFbSqlGenerationHelper : ISqlGenerationHelper
 {
-	string StringLiteralQueryType(string s);
+	string StringLiteralQueryType(string s, bool isUnicode);
 	string StringParameterQueryType(bool isUnicode);
 	void GenerateBlockParameterName(StringBuilder builder, string name);
 	string AlternativeStatementTerminator { get; }