refactor(eventhubs)!: harden public API for 1.0 (non_exhaustive + TryFrom)

[j7nw4r]

Summary

This is a BREAKING change to azure_messaging_eventhubs, intended to land before the 1.0.0 API freeze. It marks the crate's public data, options, and error types #[non_exhaustive] and converts four panicking MessageId conversions from From to TryFrom. Neither change can be made after 1.0 without a major version bump, so they are grouped here as pre-1.0 hardening.

Motivation

#[non_exhaustive] lets new fields and enum variants be added after 1.0 without breaking downstream code, which is not possible once the public surface is frozen. The four From<MessageId> impls that produced Uuid, Vec<u8>, String, and u64 panicked whenever the MessageId variant did not match the requested target type, putting a panic on an infallible-looking conversion in the public API; TryFrom surfaces the mismatch as a recoverable error instead.

Changes

• Added #[non_exhaustive] to the MessageId, StartLocation, and ProcessorStrategy enums; the SendBatchOptions, SendEventOptions, SendMessageOptions, AddEventDataOptions, EventDataBatchOptions, OpenReceiverOptions, StartPosition, and RetryOptions options structs; and the EventHubProperties, EventHubPartitionProperties, Checkpoint, Ownership, StartPositions, and EventHubsError data structs. ErrorKind and ConnectionString already had it.
• Added a Default derive to AddEventDataOptions so external code keeps a construction path now that the empty struct literal is no longer usable outside the crate. The other affected structs already derived or implemented Default.
• Changed Uuid, Vec<u8>, String, and u64 to implement TryFrom<MessageId> (with Error = EventHubsError) instead of From<MessageId>. The error reuses the crate's existing EventHubsError type to keep the public error surface unified. The infallible conversions into MessageId, and between MessageId and AmqpMessageId, remain From.
• Updated the crate's doc examples (including the README rendered into the crate docs), integration tests, examples, and benchmark to construct the now-non_exhaustive structs via Default::default() plus public-field assignment, since struct-literal and functional-record-update construction and exhaustive enum matching are no longer available to external code.
• Recorded both breaking changes under ## 0.15.0 (Unreleased) in the CHANGELOG.

Validation

• cargo build -p azure_messaging_eventhubs --all-features: pass
• cargo clippy -p azure_messaging_eventhubs --all-targets --all-features -- -D warnings: pass
• cargo test -p azure_messaging_eventhubs --all-features: pass (offline unit and doc tests; live #[recorded::test(live)] tests self-skip without credentials)
• cargo fmt -p azure_messaging_eventhubs -- --check: clean