Country region vocabulary

[leilafarsani]

Implement country-region vocabulary-based splitting

This PR implements correct handling of countries and regions according to the IATI standard:
Recipient-country documentation

When both the recipient-region and recipient-country are declared, then the @percentage values should sum to 100% per region vocabulary for the specific iati-activity.

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✅ Changes Made

• Countries and regions from the same vocabulary now form a single 100% allocation.
• Multiple region vocabularies result in independent 100% allocations.
• Percentages are normalised within each vocabulary group.
• Added vocabulary attribute to IATIActivityRecipientRegion.

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🛠 Implementation Details

• Countries are always considered part of vocabulary "1" (the default vocabulary).
• Regions can belong to any vocabulary (defaults to "1" if not specified).
• When countries and regions share a vocabulary, they are grouped for percentage-based splitting.
• Each vocabulary group forms a separate 100% allocation.

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🧪 Testing

Added five new tests to verify:

• ✅ Countries and regions in the same vocabulary are treated together.
• ✅ Splitting works across multiple region vocabularies.
• ✅ Percentages are properly normalized within vocab groups.
• ✅ Splitting when only countries are present.
• ✅ Total output can exceed original value when vocabularies are independent.

All existing tests continue to pass.

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🔗 Related Issues

Resolves #6

[jarofgreen]

In this test, there is only 1 vocabulary? And the percentages add up to 100 anyway? I think it would be a better test if both those things were changed

[jarofgreen]

Are the results correct here?

• Vocab 1, FR + GB + ASIA + AFRICA = 250 + 250 + 250 + 250 = 1000, that's good
• Vocab 2, FR + GB + NORTH + SOUTH = 25% + 25% + 50% + 50% = 150% = 250 + 250 + 500 + 500 = 1500, to much? That 150% total should have been normalised back to 100% I think?