create filter package

Author: jonhealy1

stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/filter.py

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+# STAC FastAPI Filter Package
+
+This package contains shared filter extension functionality used by both the Elasticsearch and OpenSearch
+implementations of STAC FastAPI. It helps reduce code duplication and ensures consistent behavior
+between the two implementations.
+
+## Package Structure
+
+The filter package is organized into three main modules:
+
+- **cql2.py**: Contains functions for converting CQL2 patterns to Elasticsearch/OpenSearch compatible formats
+  - [cql2_like_to_es](cci:1://file:///home/computer/Code/stac-fastapi-elasticsearch-opensearch/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/filter.py:59:0-75:5): Converts CQL2 "LIKE" characters to Elasticsearch "wildcard" characters
+  - [_replace_like_patterns](cci:1://file:///home/computer/Code/stac-fastapi-elasticsearch-opensearch/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/filter.py:51:0-56:71): Helper function for pattern replacement
+
+- **transform.py**: Contains functions for transforming CQL2 queries to Elasticsearch/OpenSearch query DSL
+  - [to_es_field](cci:1://file:///home/computer/Code/stac-fastapi-elasticsearch-opensearch/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/filter.py:83:0-93:47): Maps field names using queryables mapping
+  - [to_es](cci:1://file:///home/computer/Code/stac-fastapi-elasticsearch-opensearch/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/filter.py:96:0-201:13): Transforms CQL2 query structures to Elasticsearch/OpenSearch query DSL
+
+- **client.py**: Contains the base filter client implementation
+  - [EsAsyncBaseFiltersClient](cci:2://file:///home/computer/Code/stac-fastapi-elasticsearch-opensearch/stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/filter.py:209:0-293:25): Base class for implementing the STAC filter extension
+
+## Usage
+
+Import the necessary components from the filter package:
+
+```python
+from stac_fastapi.sfeos_helpers.filter import cql2_like_to_es, to_es, EsAsyncBaseFiltersClient

stac_fastapi/sfeos_helpers/stac_fastapi/sfeos_helpers/filter/README.md

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+"""Shared filter extension methods for stac-fastapi elasticsearch and opensearch backends.
+
+This module provides shared functionality for implementing the STAC API Filter Extension
+with Elasticsearch and OpenSearch. It includes:
+
+1. Functions for converting CQL2 queries to Elasticsearch/OpenSearch query DSL
+2. Helper functions for field mapping and query transformation
+3. Base implementation of the AsyncBaseFiltersClient for Elasticsearch/OpenSearch
+
+The filter package is organized as follows:
+- cql2.py: CQL2 pattern conversion helpers
+- transform.py: Query transformation functions
+- client.py: Filter client implementation
+
+When adding new functionality to this package, consider:
+1. Will this code be used by both Elasticsearch and OpenSearch implementations?
+2. Is the functionality stable and unlikely to diverge between implementations?
+3. Is the function well-documented with clear input/output contracts?
+
+Function Naming Conventions:
+- Function names should be descriptive and indicate their purpose
+- Parameter names should be consistent across similar functions
+"""
+
+from .client import EsAsyncBaseFiltersClient
+
+# Re-export the main functions and classes for backward compatibility
+from .cql2 import _replace_like_patterns, cql2_like_to_es
+from .transform import to_es, to_es_field
+
+__all__ = [
+    "cql2_like_to_es",
+    "_replace_like_patterns",
+    "to_es_field",
+    "to_es",
+    "EsAsyncBaseFiltersClient",
+]