FINERACT-2468: Fix datatable operations in PostgreSQL non-public schemas

Use current_schema instead of hardcoded 'public' in getTableIndexes()
and isTablePresent() methods to support multi-tenant PostgreSQL
deployments where datatables reside in tenant-specific schemas.

This fixes:
- GET /datatables returning 404 for new datatables
- Datatable save operations failing with 'Datatable not found'

Root cause: Index metadata queries were looking in 'public' schema
while table columns query correctly used current_schema, causing
inconsistent behavior in GenericDataServiceImpl.

Changes:
- PostgreSQLQueryService.getTableIndexes(): Use current_schema
- PostgreSQLQueryService.isTablePresent(): Use current_schema

Testing:
- All unit tests pass (93/93 in fineract-core)
- Manual PostgreSQL verification confirms fix works correctly

Author: AshharAhmadKhan

fineract-core/src/main/java/org/apache/fineract/infrastructure/core/service/database/PostgreSQLQueryService.java

@@ -44,8 +44,10 @@ public boolean isSupported() {
     @Override
     public boolean isTablePresent(DataSource dataSource, String tableName) {
         JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
+        // Use current_schema for consistency with getTableColumns() and getTableIndexes().
+        // This ensures tenant-specific schemas work correctly (FINERACT-2468).
         Integer result = jdbcTemplate.queryForObject(
-                "SELECT COUNT(table_name) FROM information_schema.tables " + "WHERE table_schema = 'public' AND table_name = ?",
+                "SELECT COUNT(table_name) FROM information_schema.tables " + "WHERE table_schema = current_schema AND table_name = ?",
                 Integer.class, tableName);
         return Objects.equals(result, 1);
     }
@@ -67,7 +69,10 @@ public SqlRowSet getTableColumns(DataSource dataSource, String tableName) {
     @Override
     public List<IndexDetail> getTableIndexes(DataSource dataSource, String tableName) {
         JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);
-        String sql = "SELECT indexname FROM pg_indexes WHERE schemaname = 'public' AND tablename = ?";
+        // Use current_schema instead of hardcoded 'public' to support tenant-specific schemas.
+        // This fixes datatable operations in multi-tenant PostgreSQL deployments where
+        // datatables reside in non-public schemas (FINERACT-2468).
+        String sql = "SELECT indexname FROM pg_indexes WHERE schemaname = current_schema AND tablename = ?";
         final SqlRowSet indexDefinitions = jdbcTemplate.queryForRowSet(sql, tableName); // NOSONAR
         if (indexDefinitions.next()) {
             return DatabaseIndexMapper.getIndexDetails(indexDefinitions);