feat: generate Literal type aliases instead of StrEnum classes

[vdusek]

Issue

• Closes Prefer using literal types over enums #576

Description

Replaces every generated class X(StrEnum) with a X = Literal[...] alias. Users pass plain strings (status='RUNNING') instead of enum members, the aliases are reusable across method signatures, and behavior matches Crawlee and the Apify SDK — avoiding mixing-enum-with-string footguns like #575.

Why post-processing

The natural fix — --enum-field-as-literal=all + --use-type-alias on datamodel-code-generator — only handles enums referenced from operation parameters; the rest get inlined at every reference site with no stable name to import. Filed upstream as koxudaxi/datamodel-code-generator#3104. Until that lands, scripts/postprocess_generated_models.py does the rewrite ourselves; once fixed, we can drop the post-processing.

What the post-process does

• convert_enums_to_literals — rewrites every top-level class X(StrEnum) to X = Literal[...], preserving value order and class docstring.
• deduplicate_error_type_enum — removes the duplicate inlined class Type(StrEnum) datamodel-codegen emits alongside the named ErrorType (same upstream issue), and rewires Type annotations to ErrorType. AST-based.
• split_literals_to_file — moves the 11 alias blocks into _literals_generated.py so consumers don't pull in every Pydantic model.
• snake_case_camelcase_literal_values — converts camelCase string values (StorageOwnership's 'ownedByMe'/'sharedWithMe') to snake_case and emits _<NAME>_WIRE_VALUES so resource clients can convert back to the wire format.

The hand-maintained _types.py is renamed to _literals.py for symmetry.

Consumers

• All internal code imports the aliases via TYPE_CHECKING where possible.
• dataset_collection, key_value_store_collection, request_queue_collection translate ownership back to wire format via _STORAGE_OWNERSHIP_WIRE_VALUES.
• _TERMINAL_STATUSES in _resource_client.py is derived from TerminalActorJobStatus via typing.get_args() — single source of truth.
• Docstrings, integration tests, unit tests, and the two docs/02_concepts/code/03_nested_*.py examples no longer reference .MEMBER / .MEMBER.value.

Tests

tests/unit/test_postprocess_generated_models.py covers each step independently plus a full-pipeline integration test.

Breaking change

Tracked under v3 on #576. ActorJobStatus.RUNNING and similar enum-member access no longer exists — pass the plain string instead.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.55%. Comparing base (4ca99fd) to head (965eb8b).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #759      +/-   ##
==========================================
- Coverage   95.90%   95.55%   -0.36%     
==========================================
  Files          48       49       +1     
  Lines        5228     4788     -440     
==========================================
- Hits         5014     4575     -439     
+ Misses        214      213       -1     

Flag	Coverage Δ
integration	95.55% <100.00%> (-0.36%)	⬇️

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[janbuchar]

This rename is 1) pointless and 2) wrong - the file contains non-literal types too

[janbuchar]

Please improve the name so that it's clear what is the input convention and what is on the output