Bridge new azure_core (>0.21) with the legacy crates (azure_storage, etc.)

[barabadzhi]

Feature Summary

The latest azure_core should more or less work with legacy crates that contain missing functionality.

Feature Description

We're utilizing azure_core together with several other azure_* crates, like azure_storage, etc.
And currently stuck on 0.21, because azure_core >0.21 has no clear backwards compatibility with legacy azure_* crates, making it unusable when more or less complex functionality (missing from current azure_core) is needed.

Possible solution - implement Into, From, TryFrom, etc. to bridge current primitives with legacy ones. Publish it under legacy_compat or similar feature, disabled by default.

For example, this would allow to use "new" Metadata with azure_strorage (legacy) expecting a "different" type, etc. It would ease transition to azure_core > 0.21 for real world applications.

Use Case

Real world apps using functionality from "legacy" azure_* crates.

Alternatives

Sticking to azure_core 0.21.

Additional Context

It is either impossible (intentional Rust constraint) or very cumbersome to implement the "conversion" to/from "legacy" types outside the azure_* crate.

UPD: The current stats on crates.io indicate azure_core 0.21downloads surpass all of the azure_core 0.22+ combined ca. 5-10x. Upgrading a dependency version in Rust is trivial by itself, so we can assume people are stuck with azure_core 0.21 for exactly this reason - lack of clear upgrade path/legacy_compat.

[themightychris]

Yeah I'm in this stuck bucket. It seems that azure_core 0.21/azure_identity 0.21 don't correctly support managed identities in AKS and I need to use 0.25, but my application needs to access storage buckets and the 0.21 azure_storage and azure_storage_blobs crates don't seem to be compatible with 0.25 core and identity.

Are these crates referred to as "legacy" because the plan is to replace them with different crates or bake that functionality directly into azure_core? Is there no path right now to access storage while using current versions of core/identity?

For context lakekeeper/lakekeeper#1195 is the issue I'm trying to work through

[RickWinter]

Thank you for taking the time to log this issue. Currently there is no plan for new officially supported azure_core to support the old unofficial rust crates. Overtime more and more rust crates will be added to support all of Azure.

If you had managed identity support for AKS would there be anything else blocking you from moving to the most recent core, identity, and storage crates?

//cc: @ronniegeraghty