fix(apigw-manager): parse v2 api responses

[wklken]

Summary

• Release apigw-manager as 5.0.1 and add the corresponding changelog entry.
• Add a v2 response parser for apigw-manager so successful 20x v2 responses return the data field directly, including {} and [] payloads.
• Parse non-20x v2 API responses from the error body into ApiResultError, with a status/text fallback for non-JSON responses.
• Switch core v2 sync/fetch/release/permission calls to the v2 parser and add regression coverage for success, error-body, non-JSON, and connection-error cases.
• Update resource-version existence checks to use the v2 list response shape instead of the legacy count envelope.
• Stop reading comment from v2 resource-version responses when releasing; created/latest resource-version payloads are treated as id/version-only and release comment defaults to an empty string unless passed explicitly.
• Update stage MCP server sync output handling to consume the v2 data list directly instead of unwrapping a legacy data envelope again.
• Add the required v2 applicant field when applying gateway permissions, while preserving explicit applicant values from definitions.
• Remove v1-only private helpers and tests left unused after the v2 upgrade: _call, _call_with_cache, _parse_result, and itemgetter.

Verification

• PYENV_VERSION=apigw-manager poetry check -> passed with existing metadata warnings
• PYENV_VERSION=apigw-manager PYTHONPATH=src poetry run pytest -q --ds demo.settings tests/apigw_manager/apigw/management/commands/test_create_version_and_release_apigw.py -q -> 29 passed
• PYENV_VERSION=apigw-manager PYTHONPATH=src poetry run pytest -q --ds demo.settings tests/apigw_manager/apigw/management/commands/test_apply_apigw_permissions.py -q -> 1 passed
• PYENV_VERSION=apigw-manager PYTHONPATH=src poetry run pytest -q --ds demo.settings tests/apigw_manager/apigw/management/commands/test_sync_apigw_stage_mcp_servers.py -q -> 2 passed
• PYENV_VERSION=apigw-manager PYTHONPATH=src poetry run pytest -q --ds demo.settings tests/apigw_manager/apigw/management/commands -q -> 42 passed
• PYENV_VERSION=apigw-manager PYTHONPATH=src poetry run pytest -q --ds demo.settings tests/apigw_manager/core -q -> 15 passed
• PYENV_VERSION=apigw-manager make test -> 274 passed
• PYENV_VERSION=apigw-manager poetry run mypy src/apigw_manager/apigw/management/commands/create_version_and_release_apigw.py tests/apigw_manager/apigw/management/commands/test_create_version_and_release_apigw.py -> no issues found in 2 source files
• PYENV_VERSION=apigw-manager poetry run mypy src/apigw_manager/apigw/management/commands/apply_apigw_permissions.py tests/apigw_manager/apigw/management/commands/test_apply_apigw_permissions.py -> no issues found in 2 source files
• PYENV_VERSION=apigw-manager poetry run mypy src/apigw_manager/apigw/management/commands/sync_apigw_stage_mcp_servers.py tests/apigw_manager/apigw/management/commands/test_sync_apigw_stage_mcp_servers.py -> no issues found in 2 source files
• PYENV_VERSION=apigw-manager poetry run mypy src/apigw_manager/core tests/apigw_manager/core -> no issues found in 13 source files
• git diff --check / git diff --cached --check -> passed
• PYENV_VERSION=apigw-manager make lint -> failed: no lint target in sdks/apigw-manager/Makefile or included parent Makefile
• PYENV_VERSION=apigw-manager poetry run mypy src -> failed on existing errors in untouched files: src/apigw_manager/drf/utils.py, src/apigw_manager/drf/management/commands/generate_resources_yaml.py, and src/apigw_manager/plugin/config.py

[wklken]

previous pr #279

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Found multiple compatibility issues. The upgrade is not correct yet for several v2 input/output contracts.

Findings

• Resource-version create/list flow is still using v1-shaped outputs.

create_version_and_release_apigw.py (line 89) expects list_resource_versions() to return {"count": ...}, but dashboard v2 returns data as a list of {version, comment} items from views.py (line 452) and serializers.py (line 687). After _parse_v2_result, SDK returns a list, so resource_versions["count"] will fail.

• Resource-version creation returns no data, but the command needs version. 【fix in dashboard】

The SDK later uses resource_version["version"] at create_version_and_release_apigw.py (line 133). Dashboard v2 create returns OKJsonResponse(status=201) with no data at views.py (line 464), so _parse_v2_result() returns None.

• MCP server sync is double-unwrapping data.

sync_stage_mcp_servers() now returns parsed data directly as a list, but the command still does result.get("data", []) at sync_apigw_stage_mcp_servers.py (line 36). Dashboard returns OKJsonResponse(data=output_slz.data) where output_slz.data is already the list at views.py (line 665).

• apply_apigw_permissions does not send required v2 applicant.

The v2 open apply serializer requires applicant at serializers.py (line 106), but the command only defaults target_app_code and grant_dimension at apply_apigw_permissions.py (line 31). The docs example also omits applicant at sync_apigateway.md (line 264).

• Stage creation response appears wrong on the dashboard side. 【fix in dashboard】

The dashboard saves stage, but serializes the pre-save instance at views.py (line 172). For a new stage, instance is None, while the SDK command expects result["id"] and result["name"] at sync_apigw_stage.py (line 35).