Breaking changes ADR (#6595)

### Motivation and Context

Closes #6535 

### Description

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### Contribution Checklist

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- [ ] All unit tests pass, and I have added new tests where possible
- [ ] I didn't break anyone 😄

---------

Co-authored-by: Roger Barreto <[email protected]>

docs/decisions/0045-breaking-changes-guidance.md

@@ -0,0 +1,40 @@
+---
+status: accepted
+contact: markwallace
+date: 2024-06-10
+deciders: sergeymenshykh, mbolan, rbarreto, dmytrostruk, westey
+consulted: 
+informed: 
+---
+
+# Guidance for Breaking Changes
+
+## Context and Problem Statement
+
+We must avoid breaking changes in .Net because of the well known [diamond dependency issue](https://learn.microsoft.com/en-us/dotnet/standard/library-guidance/dependencies#diamond-dependencies) where breaking changes between different versions of the same package cause bugs and exceptions at run time.
+
+## Decision Drivers
+
+Breaking changes are only allowed under the following circumstances:
+
+- Updates to an experimental feature i.e. we have learnt something new and need to modify the design of an experimental feature.
+- When one of our dependencies introduces an unavoidable breaking change.
+
+All breaking changes must be clearly documented, definitely in the release notes and possibly also via a migration guide Blog post.
+
+- Include a detailed description of the breaking change in the PR description so that it is included in the release notes.
+- Update Learn Site migration guide documentation and have this published to coincide with the release which includes the breaking change.
+
+In all other cases we must avoid breaking changes. There will be situations where we need to move to accommodate a change to one of our dependencies or introduce a new capability e.g.
+
+- When we find a security issue or a severe bug (e.g. data loss).
+- One of our dependencies introduces a major breaking change e.g. the introduction of the new OpenAI SDK.
+- When we find a severe limitation in our current implementation e.g. when the AI services introduce a new capability.
+
+In these cases we will plan to obsolete the API(s) and provide a documented migration path to the new preferred pattern.
+An example of this will be the switch to the new OpenAI .Net SDK.
+During this transition there will be a period where the new and old API's will be supported to allow customers to migrate.
+
+## Decision Outcome
+
+Chosen option: We must avoid breaking changes in .Net because of the well known diamond dependency issue.