[iliazintchenko]

Summary

• add semi-monthly to the v3 recurrence periodicity enum
• align compound recurrence values with the API’s hyphenated wire format
• continue accepting legacy underscore spellings
• bump the SDK to 5.6.0

Validation

• 11 focused tests passed on Pydantic 1.10
• 11 focused tests passed on Pydantic 2
• package build succeeded
• focused lint and diff checks passed

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Note

Medium Risk
Enum .value strings change for existing compound periodicities, which can break strict string comparisons; parsing remains backward compatible via _missing_.

Overview
Releases 5.6.0 with v3 recurrence updates: semi-monthly is added to RecurrencePeriodicity, and compound frequencies now use the API’s hyphenated strings (bi-weekly, bi-monthly, semi-yearly) instead of underscores.

A _missing_ hook on the enum still accepts legacy underscore spellings when parsing, while serialization and .value follow the wire format. CHANGELOG documents the release; focused tests cover enum parsing, RecurrenceGroup JSON round-trip, and sync/async recurring_groups responses for semi-monthly.

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