fix: Fix private key normalization error and raise a clear ValueError instead of a pyasn1 error when a private key cannot be loaded

[coo-mdsol]

• Fix to_rsa_format wrapping non-PEM values (such as a KMS-encrypted key) in
  -----BEGIN RSA PRIVATE KEY----- markers, which made lambda_helper skip KMS
  decryption and pass the ciphertext to the RSA loader
• Fix loading of private keys stored as one-liners with escaped \n (or \r\n) sequences,
  which previously corrupted the base64 body and raised a pyasn1 decoding error
• Fix mauth_client.lambda_helper mangling PKCS#8 (-----BEGIN PRIVATE KEY-----) keys
• Raise a clear ValueError instead of a pyasn1 error when a private key cannot be loaded

[Copilot]

🟡 Changes recommended

Add the missing malformed-PEM error regression test and correct the changelog version heading.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Fixes private-key normalization and loading failures in standard and AWS Lambda configurations.

Changes:

• Preserves KMS-encrypted values and normalizes escaped newlines.
• Supports PKCS#1 and PKCS#8 keys.
• Converts pyasn1 failures into clear ValueErrors.
• Adds regression coverage and bumps the patch version.

File summaries

File	Description
tests/utils_test.py	Tests private-key normalization scenarios.
tests/lambda_helper_test.py	Tests Lambda key handling and KMS decryption.
pyproject.toml	Bumps the package version to 1.10.1.
mauth_client/utils.py	Improves PEM detection and escaped-newline normalization.
mauth_client/rsa_signer.py	Translates pyasn1 failures to ValueError; malformed-PEM regression coverage is still needed.
mauth_client/lambda_helper.py	Handles encrypted values and PKCS#8 keys correctly.
CHANGELOG.md	Documents the release; the version heading should be corrected to 1.10.1.

Review details

• Files reviewed: 7/7 changed files
• Comments generated: 2
• Review effort level: Balanced

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