docs: Fix version 0.19.x redirects (#6128)

* docs: Fix version 0.19.x redirects

* docs: Adds architecture and Terraform redirects

* docs: Main install topics

* docs: Integrations and operations

* docs: Fixes remaining 0.19.x redirects

* docs: Updates reference doc page

* docs: Fixes

website/content/docs/index.mdx

@@ -4,11 +4,11 @@ page_title: Documentation
 description: Boundary reference documentation
 ---
 
-# Boundary Reference Documentation
+# Boundary reference documentation
 
-Welcome to the Boundary reference documentation! The documentation is reference
+Welcome to the Boundary reference documentation. The documentation is reference
 material for Boundary's concepts and available features.
 
-- Get started using Boundary with our [step-by-step onboarding tutorial](/boundary/tutorials) at HashiCorp Learn.
-- Install Boundary by using a precompiled binary or building from source with the documentation [here](/boundary/docs/getting-started/)
-- Learn about Boundary's [core concepts](/boundary/docs/concepts/) for how identities, permissions, and resources are organized.
+- Get started using Boundary with our [step-by-step onboarding tutorials](/boundary/tutorials).
+- Deploy Boundary in a [self-managed environment](/boundary/docs/deploy/self-managed) or on the [HashiCorp Cloud Platform (HCP)](/boundary/docs/hcp/get-started/deploy-and-login).
+- Learn about [what Boundary is](/boundary/docs/what-is-boundary/) or refer to the [domain model](/boundary/docs/domain-model) to understand how identities, permissions, and resources are organized.