FEAT: Make _bulkcopy a public API (#449)

…or missing mssql_py_core

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> GitHub Issue: #448

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This change renames `_bulkcopy` to `bulkcopy` to make the feature
available in the public API surface area.

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FEAT: Expose `bulkcopy` API

Change error message to reflect that the absence of mssql_py_core is an
internal error

Author: saurabh500

mssql_python/cursor.py

@@ -2499,7 +2499,7 @@ def nextset(self) -> Union[bool, None]:
         return True
 
     # ── Mapping from ODBC connection-string keywords (lowercase, as _parse returns)
-    def _bulkcopy(
+    def bulkcopy(
         self,
         table_name: str,
         data: Iterable[Union[Tuple, List]],
@@ -2579,8 +2579,8 @@ def _bulkcopy(
             import mssql_py_core
         except ImportError as exc:
             raise ImportError(
-                "Bulk copy requires the mssql_py_core library which is not installed. "
-                "To install, run: pip install mssql_py_core "
+                "Bulk copy requires the mssql_py_core library which is not available. "
+                "This is an unexpected error. "
             ) from exc
 
         # Validate inputs

tests/test_019_bulkcopy.py

@@ -65,7 +65,7 @@ def test_bulkcopy_basic(cursor):
 
     # Perform bulkcopy with auto-mapping (no column_mappings specified)
     # Using explicit timeout parameter instead of kwargs
-    result = cursor._bulkcopy(table_name, data, timeout=60)
+    result = cursor.bulkcopy(table_name, data, timeout=60)
 
     # Verify result
     assert result is not None