Add validation process documentation to getting started guide (#2966)

This pull request enhances the Azure DevOps Migration Tools
documentation by introducing and emphasizing a new "Validation Process"
section. The main goal is to guide users through the built-in validation
steps that help catch configuration and data issues early, improving
migration reliability and reducing errors.

**New Validation Process Documentation:**

* Added a dedicated `validation` page that explains the two-step
validation process (pre-data-load and post-data-load), detailing the
roles of `TfsWorkItemTypeValidatorTool` and
`TfsValidateRequiredFieldTool`. This helps users understand how to
verify their setup before migrating data.

**References and Guidance Updates:**

* Added a prominent note and section to the getting started guide,
directing users to review the new validation process documentation
before beginning migration. This helps prevent common mistakes and saves
time.
* Updated troubleshooting advice to include a link to the validation
process documentation, ensuring users are aware of the full validation
workflow and resources available.

Author: MrHinsh

docs/content/docs/get-started/getting-started/index.md

@@ -19,6 +19,11 @@ Watch the [Video Overview](https://youtu.be/RCJsST0xBCE) to get started in 30 mi
 2. Check that you have the required [Permissions]({{< ref "docs/setup/permissions" >}}) to run the tools.
 3. Get to grips with the [Configuration]({{< ref "docs/reference" >}}) to understand how to configure the tool. (you can skip this for now and come back to it later)
 
+
+## Validation Process
+
+> **Before you begin migration, review the [Validation Process documentation]({{< ref "docs/get-started/validation" >}}) to understand how the tools automatically check your configuration and data for common issues. This can save you significant time and help avoid common migration errors.**
+
 ## Getting Started
 
 This is going to be a crash course and I really recommend watching [What can go wrong and what can go right with a migration via Azure DevOps](https://youtu.be/3jYFD-6_kZk?si=xxvBoljBWjGAOVuv) and then [Basic Work Item Migration with the Azure DevOps Migration Tools](https://youtu.be/Qt1Ywu_KLrc?si=uEXjLS2pwe244ugV) before you get started! This will prep you for the journey ahead.
@@ -106,6 +111,9 @@ Missing field 'Microsoft.VSTS.Common.CustomField' in 'User Story'.
 - **Solution 2:** Configure field mapping to map to an existing field
 - **Solution 3:** Exclude the field from validation if it's not needed
 
+
+For a complete overview of the validation process—including both pre-migration and pre-data-load validation steps—see the [Validation Process documentation]({{< ref "docs/get-started/validation" >}}).
+
 For detailed troubleshooting and configuration options, see the [TfsWorkItemTypeValidatorTool documentation]({{< ref "docs/reference/tools/tfsworkitemtypevalidatortool" >}}).
 
 **Remember:** If you want a processor to run, its `Enabled` attribute must be set to `true`.

docs/content/docs/get-started/validation/index.md

@@ -0,0 +1,39 @@
+---
+title: "Validating your Azure DevOps Migration Tools migration"
+description: This tutorial covers the steps to validate and verify your migration using the Azure DevOps Migration Tools.
+short_title: Get Validated
+weight: 10
+aliases:
+  - /validation/
+date: 2025-09-01T09:00:00Z
+
+---
+
+The Azure DevOps Migration Tools use a two-step validation process to ensure a smooth and successful migration. This process helps catch configuration or data issues early, saving time and preventing unnecessary data loading when migration cannot proceed.
+
+## 1. Pre-Data-Load Validation
+
+Before any data is loaded, the tool runs the [`TfsWorkItemTypeValidatorTool`]({{< ref "/docs/reference/tools/tfsworkitemtypevalidatortool/" >}}). This validator checks that all required work item types exist and are correctly mapped between the source and target systems. If any issues are found at this stage, the migration process stops immediately, preventing wasted effort on loading data that cannot be migrated.
+
+**Key Points:**
+- Ensures work item types are valid and mapped before loading data
+- Prevents unnecessary data processing if migration cannot continue
+- Fast feedback for configuration issues
+
+
+## 2. Post-Data-Load Validation (Before Migration)
+
+Before any data is actually migrated, the [`TfsValidateRequiredFieldTool`]({{< ref "/docs/reference/tools/tfsvalidaterequiredfieldtool/" >}}) runs. This validator checks that all required fields are present and populated in the data to be migrated. Running this validation step before migration helps minimize errors and ensures that the migration process will not fail due to missing or incomplete required fields.
+
+**Key Points:**
+- Validates required fields before migration begins
+- Ensures all work items to be migrated meet requirements
+- Minimizes migration errors by catching issues early
+
+## Why This Matters
+
+By running validation both before and after data loading, the migration process minimizes wasted effort and maximizes the chances of a successful migration. Early detection of issues allows for quick resolution, while post-load validation ensures data quality and compliance.
+
+For more details on each validator, see their dedicated documentation pages:
+- [`TfsWorkItemTypeValidatorTool`]({{< ref "/docs/reference/tools/tfsworkitemtypevalidatortool/" >}})
+- [`TfsValidateRequiredFieldTool`]({{< ref "/docs/reference/tools/tfsvalidaterequiredfieldtool/" >}})