CORE-3868: Replace PopularCombination schema with session-ready combinations

[Rodnyy]

Link to JIRA ticket

Why

The PopularCombination endpoint never shipped (fujin has always returned Unimplemented), and its response shape — a list of markets — would force clients to re-assemble selections themselves. The quick-picks product needs the offer to be one-click creatable: the client must be able to echo the offer straight into SessionCreateRequest without any assembly of its own.

What

PopularCombinationResponse is replaced without a migration path (no producer ever emitted the old shape):

• combinations — each entry carries selection_ids in the exact SessionCreateRequest.selection_ids format, total odds (×10 000, same convention as the session protos) and raw_probability (pre-margin, 0.0–1.0).
• The old repeated PopularCombinationMarket markets = 1 field is deleted; field number and name are reserved — kollector v0.7.0 has compiled (dead) references to the old shape, and reserving keeps a stale decoder failing soft instead of hitting a wire-type mismatch if the number were reused.
• Generated bindings regenerated for all languages (go/java/js/python).

After merge

Tag v0.9.0 — fujin's PopularCombination implementation (CORE-3868) depends on it, and kollector's next obbschema bump must drop its dead PopularCombinationMarket scaffolding.

[Copilot]

Pull request overview

This PR updates the PopularCombinationResponse protobuf schema to return session-ready selection combinations (directly usable in SessionCreateRequest), replacing the previously unused “markets list” shape while reserving the old field name/number to avoid accidental reuse.

Changes:

• Replaces PopularCombinationResponse.markets (field 1) with PopularCombinationResponse.combinations (field 2) and reserves field number/name 1/"markets".
• Introduces PopularCombination message containing selection_ids, odds (×10,000), and raw_probability.
• Regenerates language bindings for Go/Java/JS/Python to match the updated schema.

Reviewed changes

Copilot reviewed 2 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
proto/obb/popular.proto	Updates the protobuf schema: reserves legacy markets field and adds combinations + PopularCombination message.
go/obb/popular.pb.go	Regenerates Go bindings to expose Combinations and the new PopularCombination message fields.
java/src/main/java/com/oddin/obb/Popular.java	Regenerates Java bindings replacing markets accessors/types with combinations and new message structure.
js/obb/popular_pb.js	Regenerates JS bindings to replace PopularCombinationMarket with PopularCombination and wire field 2 for combinations.
js/obb/popular_pb.d.ts	Updates TS declarations for the new PopularCombinationResponse and PopularCombination APIs.
python/obb/popular_pb2.py	Regenerates Python bindings to match the updated descriptor (new message + reserved legacy field).

Files not reviewed (3)

• go/obb/popular.pb.go: Generated file
• java/src/main/java/com/oddin/obb/Popular.java: Generated file
• python/obb/popular_pb2.py: Generated file

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[stetinatomas-oddin]

LGTM. Clean replacement. Reserving both the old field number (1) and the name (markets) is the right call given kollector still carries compiled references to the old shape — a stale decoder then fails soft instead of risking a wire-type collision if 1 were ever reused. The new combinations shape is session-ready (selection IDs in the exact SessionCreateRequest format, odds x10000 matching the session protos, raw probability pre-margin), which is exactly what the one-click quick-picks flow needs, and bindings are regenerated across all languages. No migration concern since the endpoint never shipped.

Only follow-up is the coordination already in the description: tag v0.9.0 after merge so the fujin side can pin it.

Co-Authored-By: Claude Opus 4.8 (1M context)