Feat: microgen - adds _client_helpers.py.j2 template (#2299)

* chore: removes old proof of concept

* removes old __init__.py

* Adds two utility files to handle basic tasks

* Adds a configuration file for the microgenerator

* Removes unused comment

* chore: adds noxfile.py for the microgenerator

* feat: microgen - adds two init file templates

* feat: adds _helpers.py.js  template

* Updates with two usage examples

* feat: adds two partial templates for creating method signatures

* feat: Add microgenerator __init__.py

Migrates the empty __init__.py file to the microgenerator package.

* feat: Add AST analysis utilities

Introduces the CodeAnalyzer class and helper functions for parsing Python code using the ast module. This provides the foundation for understanding service client structures.

* feat: Add source file analysis capabilities
    Implements functions to analyze Python source files, including:
    - Filtering classes and methods based on configuration.
    - Building a schema of request classes and their arguments.
    - Processing service client files to extract relevant information.

* feat: adds code generation logic

* removes extraneous content

* feat: microgen - adds code generation logic

* feat: microgen - adds main execution and post-processing logic

* minor tweak to markers

* feat: Add testing directory\n\nAdds the scripts/microgenerator/testing directory.

* feat: Enhance to_snake_case to handle acronyms\n\nImproves the to_snake_case function in name_utils.py to correctly convert PascalCase names containing acronyms to snake_case.

* feat: Add client.py.j2 template\n\nAdds the main Jinja2 template for generating the BigQueryClient class.

* feat: Add _client_helpers.j2 partial template\n\nAdds a Jinja2 partial template containing helper macros for the client generation.

* Update scripts/microgenerator/testing/constraints-3.13.txt

* Update scripts/microgenerator/generate.py

* Update scripts/microgenerator/generate.py

Author: chalmerlowe

scripts/microgenerator/templates/partials/_client_helpers.j2

@@ -0,0 +1,49 @@
+    {#
+    This is a partial template file intended to be included in other templates.
+    It contains helper methods for the BigQueryClient class.
+    #}
+    
+    # --- HELPER METHODS ---
+    def _parse_dataset_path(self, dataset_path: str) -> Tuple[Optional[str], str]:
+        """
+        Helper to parse project_id and/or dataset_id from a string identifier.
+    
+        Args:
+            dataset_path: A string in the format 'project_id.dataset_id' or
+                'dataset_id'.
+    
+        Returns:
+            A tuple of (project_id, dataset_id).
+        """
+        if "." in dataset_path:
+            # Use rsplit to handle legacy paths like `google.com:my-project.my_dataset`.
+            project_id, dataset_id = dataset_path.rsplit(".", 1)
+            return project_id, dataset_id
+        return self.project, dataset_path
+    
+    def _parse_dataset_id_to_dict(self, dataset_id: "DatasetIdentifier") -> dict:
+        """
+        Helper to create a dictionary from a project_id and dataset_id to pass
+        internally between helper functions.
+    
+        Args:
+            dataset_id: A string or DatasetReference.
+    
+        Returns:
+            A dict of {"project_id": project_id, "dataset_id": dataset_id_str }.
+        """
+        if isinstance(dataset_id, str):
+            project_id, dataset_id_str = self._parse_dataset_path(dataset_id)
+            return {"project_id": project_id, "dataset_id": dataset_id_str}
+        elif isinstance(dataset_id, dataset_reference.DatasetReference):
+            return {
+                "project_id": dataset_id.project_id,
+                "dataset_id": dataset_id.dataset_id,
+            }
+        else:
+            raise TypeError(f"Invalid type for dataset_id: {type(dataset_id)}")
+    
+    def _parse_project_id_to_dict(self, project_id: Optional[str] = None) -> dict:
+        """Helper to create a request dictionary from a project_id."""
+        final_project_id = project_id or self.project
+        return {"project_id": final_project_id}