chore: allow optional whitespace around parameters similar to other language implementations

[sungwy]

Reference: apache/iceberg#16798

Rationale for this change

PyIceberg is a bit more strict in its parsing than the other language implementations. This allows json string representations like decimal( 9, 2 ) like the other libraries.

Are these changes tested?

Unit tested

Are there any user-facing changes?

Yes, more permissive metadata parsing by PyIceberg clients.

[Copilot]

Pull request overview

This PR makes PyIceberg’s decimal type parsing more permissive by allowing optional whitespace around decimal parameters, aligning behavior with other Iceberg language implementations.

Changes:

• Update the decimal type parsing regex to tolerate whitespace around precision/scale and separators.
• Add unit tests covering multiple whitespace variants for decimal(P,S) JSON deserialization.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/test_types.py	Adds parametrized tests to ensure DecimalType deserialization accepts optional whitespace variants.
pyiceberg/types.py	Relaxes the decimal parsing regex to allow whitespace around precision/scale and punctuation.

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[geruh]

Should we align this logic to the other regex too?

https://github.com/apache/iceberg/blob/41c8ee43b46017843b304241d250737fd10837af/api/src/main/java/org/apache/iceberg/types/Types.java#L66-L73

  private static final Pattern FIXED = Pattern.compile("fixed\\[\\s*(\\d+)\\s*\\]");
  private static final Pattern GEOMETRY_PARAMETERS =
      Pattern.compile("geometry\\s*(?:\\(\\s*([^)]*?)\\s*\\))?", Pattern.CASE_INSENSITIVE);
  private static final Pattern GEOGRAPHY_PARAMETERS =
      Pattern.compile(
          "geography\\s*(?:\\(\\s*([^,]*?)\\s*(?:,\\s*(\\w*)\\s*)?\\))?", Pattern.CASE_INSENSITIVE);
  private static final Pattern DECIMAL =
      Pattern.compile("decimal\\(\\s*(\\d+)\\s*,\\s*(\\d+)\\s*\\)");