feat: batch milestone note retrieval across multiple shipments

[shakurJJ]

Summary

get_milestone_notes returns notes for one shipment/milestone at a time. A supplier or admin dashboard covering many shipments has to call it once per shipment. This proposes a batch query.

Proposed Behaviour

• New read-only function accepting a list of shipment IDs and returning each shipment's milestone notes together.
• No change to how notes are written (add_milestone_note unchanged); this is a query-side convenience only.

Acceptance Criteria

• New batch query returns notes for multiple shipments in one call
• Behaviour for a single shipment matches what get_milestone_notes returns today
• Handles a mix of shipments with and without notes
• Tests cover single, multiple, and empty-notes cases

[dollfins]

@dollfins has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I would like to implement the new batch query function to allow for efficient retrieval of milestone notes across multiple shipment IDs. I plan to ensure the output structure remains consistent with the existing get_milestone_notes function while adding test cases to verify behavior for shipments that contain no notes.

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[Oluwasegun6921]

@Oluwasegun6921 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello Maintainer, I’d appreciate the opportunity to work on this issue. I can start right away and handle it carefully.

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[Udokwuebube]

@Udokwuebube has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

hi, i would like to work on this.

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[Thomson-dev]

@Thomson-dev has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

pls can work I on this issue

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[Mubking-dev]

@Mubking-dev has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hey, can I pick this up?
Right now you’re stuck calling get_milestone_notes for each shipment. I’ll add a batch read so you can grab notes for multiple shipments in one go. Won’t touch how notes are written. I’ll test it for single, multiple, and empty cases and make sure it plays nice with the existing flow.

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