Add mysql_fdw for MySQL/Doris support (supabase#584)

* Add mysql_fdw for MySQL/Doris support via text protocol

Uses mysql_async crate with text protocol (simple_query) instead of
prepared statements, which makes it compatible with Doris and other
MySQL-protocol databases that don't support mysql_stmt_result_metadata.

Based on mssql_fdw template with MySQL-specific adaptations:
- MySQL LIMIT without requiring ORDER BY
- String-based date/time parsing for broader compatibility
- Support for conn_string and conn_string_id (vault) options

* fix: update mysql_fdw website URL to upstream repo path

* fix: address CodeRabbit review feedback for mysql_fdw

- Add mysql_fdw to native_fdws feature list in Cargo.toml
- Preserve SQLSTATE codes for OptionsError/CreateRuntimeError and
  sanitize mysql_async error messages to avoid leaking credentials
- Propagate datetime/date parse errors instead of silently returning NULL
- Quote SQL identifiers with backticks to prevent injection and
  reserved word conflicts

* fix: use MySQL-safe cell formatter for WHERE clause values

Add MysqlCellFormatter that escapes single quotes and backslashes in
string literals, and formats booleans as 0/1 for MySQL compatibility.
Use deparse_with_fmt instead of deparse to apply the safe formatter
when building WHERE predicates.

* fix: inline format args to satisfy clippy uninlined_format_args

* fix: address PR review - vault error propagation, identifier quoting in WHERE, and DML support

- Replace get_vault_secret().unwrap_or_default() with proper error propagation
  so missing/failed vault lookups surface as errors instead of empty conn_str
- Add custom deparse_qual() that quotes field names with backticks in WHERE
  clauses, matching the quoting used in SELECT columns and ORDER BY
- Implement DML methods (begin_modify, insert, update, delete, end_modify)
  using the same runtime/connection pattern as begin_scan

* feat: add streaming support and test cases

* feat(mysql_fdw): enhance schema import and add CRUD tests for MySQL integration

* feat(mysql_fdw): enhance user table schema and add additional data validation tests

* feat(mysql_fdw): add MySQL foreign data wrapper documentation and support for JSON data type

* fix(mysql.md): update author information and change tags from official to community

---------

Co-authored-by: Bo Lu <[email protected]>

Author: wenerme

Cargo.lock

@@ -22,6 +22,7 @@
 | [HubSpot](./wasm-wrappers/fdw/hubspot_fdw)      | A Wasm FDW for [HubSpot](https://www.hubspot.com/)                            | ✅   | ❌     |
 | [Infura](./wasm-wrappers/fdw/infura_fdw)        | A Wasm FDW for [Infura](https://www.infura.io/) blockchain data               | ✅   | ❌     |
 | [Logflare](./wrappers/src/fdw/logflare_fdw)     | A FDW for [Logflare](https://logflare.app/)                                   | ✅   | ❌     |
+| [MySQL](./wrappers/src/fdw/mysql_fdw)           | A FDW for [MySQL](https://www.mysql.com/)                                     | ✅   | ✅     |
 | [Notion](./wasm-wrappers/fdw/notion_fdw)        | A Wasm FDW for [Notion](https://www.notion.so/)                               | ✅   | ❌     |
 | [OpenAPI](./wasm-wrappers/fdw/openapi_fdw)      | A Wasm FDW for any [OpenAPI](https://www.openapis.org/) 3.0+ REST API         | ✅   | ❌     |
 | [Orb](./wasm-wrappers/fdw/orb_fdw)              | A Wasm FDW for [Orb](https://www.withorb.com/)                                | ✅   | ❌     |

README.md

@@ -27,6 +27,7 @@ Each FDW documentation includes a detailed "Limitations" section that describes
 | Infura        |   ✅   |   ❌   |   ❌   |   ❌   |    ❌    |    ✅     |
 | Iceberg       |   ✅   |   ✅   |   ❌   |   ❌   |    ❌    |    ❌     |
 | Logflare      |   ✅   |   ❌   |   ❌   |   ❌   |    ❌    |    ❌     |
+| MySQL         |   ✅   |   ✅   |   ✅   |   ✅   |    ❌    |    ✅     |
 | Notion        |   ✅   |   ❌   |   ❌   |   ❌   |    ❌    |    ❌     |
 | OpenAPI       |   ✅   |   ❌   |   ❌   |   ❌   |    ❌    |    ❌     |
 | Orb           |   ✅   |   ✅   |   ✅   |   ✅   |    ❌    |    ✅     |