Initial pass of versioning guidelines (#564)

* Initial pass of versioning guidelines
* Apply suggestions from PR review

Co-authored-by: Jeffrey Richter <[email protected]>

azure/VersioningGuidelines.md

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+# Azure Versioning Guidelines
+
+## History
+
+<details>
+  <summary>Expand change history</summary>
+
+| Date        | Notes                                                          |
+| ----------- | -------------------------------------------------------------- |
+| 2024-Nov-14 | Azure Service Versioning & Breaking Change Guidelines       |
+
+</details>
+
+## Guidelines
+
+This document provides a "Dos and Don'ts" list for complying with the Azure Versioning and Breaking Change Policy,
+as documented [internally](aka.ms/AzBreakingChangesPolicy) and [externally](https://learn.microsoft.com/azure/developer/intro/azure-service-sdk-tool-versioning).
+
+:white_check_mark: **DO** thoroughly ensure/test the API contract is entirely correct before merging it into a production branch of the specs repo.
+
+Testing helps avoid "BugFix" changes to the API definition. Testing should be done at the HTTP level as well as through generated SDKs.
+
+:white_check_mark: **DO** retire all prior preview API versions 90 days after a new GA or preview API version is released.
+
+:white_check_mark: **DO** contact the Azure Breaking Change Review board to coordinate communications to customers
+when releasing an API version requiring the retirement of a prior version.
+
+:white_check_mark: **DO** create a new preview API version for any features that should remain in preview following a new GA release.
+
+:white_check_mark: **DO** use a date strictly later than the most recent GA API version when releasing
+a new preview API version.
+
+:white_check_mark: **DO** deprovision any API version that has been retired. Retired APIs versions should behave like
+an unknown API version (see [ref](https://aka.ms/azapi/guidelines#versioning-api-version-unsupported)).
+
+:white_check_mark: **DO** remove retired API versions from the azure-rest-api-specs repo.
+
+:white_check_mark: **DO** review any change to service behavior that could disrupt customers with the Azure Breaking Changes review board, even if the change is not part of the API definition.
+
+Some examples of behavior changes that must be reviewed are:
+- Introducing or changing rate limits to be more restrictive than previously
+- Changing the permissions required to successfully execute an operation
+
+:no_entry: **DO NOT** change the behavior of an API version that is available to customers either in public preview or GA.
+Changes in behavior should always be introduced in a new API version, with prior versions working as before.
+
+:no_entry: **DO NOT** introduce breaking changes from a prior GA version just to satisfy ARM or Azure API guidelines.
+
+Avoiding breaking changes in a GA API takes precedence over adherence to API guidelines and resolving linter errors.
+
+:no_entry: **DO NOT** keep a preview feature in preview for more than 1 year; it must go GA (or be removed) within 1 year after introduction.