* `execute_script()` now returns a boolean for error handling.
* Added transaction to `Migration_MissingConfigKeys.up()`.
* Added `executeScriptWithTransaction()` to migration helpers.
* Many changes for testing; also minor formatting fixes.
* Removed test code and pointed the `NullableTaxCategoryId` migration at the right SQL file.
* Fixed header.php
* Code cleanup from code review:
- Added IGNORE to SQL scripts.
- Added try-catch to executeScriptWithTransaction().
- Various comment changes.
* Fixed naming issue
Nullable tax category ID migration now runs the correct script.
* Updated SQL
Replaced INSERT WHERE NOT EXISTS in missing config keys sql script to use a single INSERT IGNORE.
* Updated migration helper
Updated executeScriptWithTransaction to use transRollback
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Co-authored-by: Joe Williams <hey-there-joe@outlook.com>
