fix(idempotency): validate idempotency record returned in conditional write

[dreamorosi]

Description of your changes

This PR fixes a bug that was introduced in the last release and that caused the Idempotency utility to skip the validation of a payload on subsequent requests.

In order to leverage the new capability of ConditionalCheckFailedException to return the item that made the conditional check to fail, we had to implement a logic that sort of looks like this:

flowchart LR
    A[saveRecord] -->|ConditionalWrite| B{is new SDK}
    B -->|Yes| C[throw IdempotencyItemAlreadyExistsError with IdempotencyRecord]
    B -->|No| D[throw IdempotencyItemAlreadyExistsError  only]

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The pseudo-saveRecord from the chart above is called by the IdempotencyHandler, which handled it this way:

flowchart LR
    A[catch IdempotencyItemAlreadyExistsError] --> B{does it have IdempotencyRecord?}
    B -->|Yes| C[use it as is]
    C --> H[carry on]
    B -->|No| E[read record from DDB]
    E --> F[validate current request vs stored record]
    F --> G{do they match}
    G -->|Yes| H
    G -->|No| I[throw IdempotencyValidationError]

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As you can see from the flow above, in one of the paths the payload was never validated.

This PR changes the access property of the validatePayload method from private to public so that it's exposed on the persistence layer and can be called directly by the IdempotencyHandler.

The flow now looks like this:

flowchart LR
    A[catch IdempotencyItemAlreadyExistsError] --> B{does it have IdempotencyRecord?}
    B -->|Yes| C[validate payload]
    C --> G
    B -->|No| E[read record from DDB]
    E --> F[validate current request vs stored record]
    F --> G{do they match}
    G -->|Yes| H[carry on]
    G -->|No| I[throw IdempotencyValidationError]

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Related issues, RFCs

Issue number: #2058

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my change is effective and works
• The PR title follows the conventional commit semantics

Breaking change checklist

Is it a breaking change?: NO

• I have documented the migration process
• I have added, implemented necessary warnings (if it can live side by side)

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[dreamorosi]

Adding this for visibility: aws-powertools/powertools-lambda-python#3781

[kevin-secrist]

Thanks for implementing this bugfix so quickly! I left a comment on some logic that may be good to include here as well, or potentially as a separate PR.

[heitorlessa]

suuuperb!

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

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