Docs/migration 1x to 2x

[ayushiahjolia]

Issue #, if available: N/A

Description of changes:
Migration guide for python v2

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[github-actions]

Codex AI review

No actionable findings. Changes are documentation-only; residual risk is limited to future API/documentation drift.

Reviewed commit 6c1c23fe6206a4982795f437c0e251941292116b. Workflow run

[github-actions]

Claude AI review

Documentation-only PR: a new docs/migration-1.x-to-2.x.md migration guide and an expanded WaitForConditionConfig docstring in packages/aws-durable-execution-sdk-python/src/aws_durable_execution_sdk_python/waits.py.

I verified the guide's technical claims against the source rather than reviewing runtime behavior, since inaccurate migration docs would misdirect users:

• Error hierarchy / exports — DurableOperationError base, StepError/InvokeError/ChildContextError/WaitForConditionError, graded CallbackError subtypes, SerDesError (child of DurableExecutionsError), RetryableSerDesError (retryable InvocationError); all root exports match __init__.py __all__.
• __cause__ — raise_as_operation_error reconstructs a DurableOperationError stand-in (registry fallback to base for non-SDK types) on both first run and replay; the guide's claim is accurate.
• First-run round trip — confirmed in step.py, child.py, wait_for_condition.py; invoke.py does not round-trip, matching "invoke unaffected."
• wait_for_condition — initial_state round-tripped before first check; empty-string payload treated as no stored state, restarting from initial_state.
• wait_for_callback serdes — enclosing child context uses default extended-type serdes, distinct from WaitForCallbackConfig.serdes.
• Completion predicate / BatchResult — should_complete, complete_batch/continue_batch, BatchCompletionError (only CUSTOM_COMPLETION_FAILED), throw_if_error typed raises, and fail-fast map/parallel defaults all match.
• attempt field — required no-default field on StepContext and WaitForConditionCheckContext.
• Removed names — CallableRuntimeError, WaitDecision, ItemBatcher, WaitStrategyConfig.timeout*, etc. confirmed absent.

No inaccurate statements or broken examples found. No actionable findings.

Residual test risk: the guide's code snippets and rg helpers are not covered by doctests/CI, so future API drift wouldn't be caught automatically — acceptable for a docs-only change. Separately (out of scope, not in this diff): the pre-existing DurableOperationError docstring at packages/aws-durable-execution-sdk-python/src/aws_durable_execution_sdk_python/exceptions.py:268-269 states the escaping error "is preserved as __cause__ on the first run," which contradicts the actual reconstruction behavior the new guide correctly documents.

Reviewed commit 6c1c23fe6206a4982795f437c0e251941292116b. Workflow run

[zhongkechen]

New features belong elsewhere, don't they?

[yaythomas]

empy str payloads? 1.x dropped them when serializing; 2.x preserves them (b448f3e). A workflow that observed None in 1.x can observe "" in 2.x.

[yaythomas]

To help w seo and instead of table (formatting on table for longer text can be limiting)... taking example from https://github.com/aws/aws-sdk-js-v3/blob/main/UPGRADING.md or https://docs.python.org/3/whatsnew/3.12.html#porting-to-python-3-12, how about a

## Porting to 2.0
### CallableruntimeErrror removed
<<before>>.
<<after>>
Catch `StepError`, `InvokeError`, `ChildContextError`, or `WaitForConditionError` (or the base `DurableOperationError`) instead of `CallableRuntimeError`. 

### Remove x
<<before>>
<<after>>

this also makes it more feasible to have meaningful little code snippets in triple backticks etc.