[BYOIP] Introduce service bindings and link to API (#17220)

* Bring index.md from previous full-fledged PR

* Move index.mdx into its own page and remove reference to guide

* Apply suggestions from code review

Co-authored-by: Pedro Sousa <[email protected]>

---------

Co-authored-by: Pedro Sousa <[email protected]>

Author: 2 people

src/content/docs/byoip/service-bindings.mdx

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+---
+title: IP address service bindings
+pcx_content_type: concept
+sidebar:
+  order: 6
+  label: Service bindings
+description: In IP address management, service binding refers to the association of IPs to specific Cloudflare services. Review the available options and the API endpoints to set up service bindings.
+---
+
+Within IP address management, service binding refers to the association of an IP (or a range of IPs) to specific Cloudflare services.
+
+:::note
+Service binding operations are currently only available via API. You can find all endpoints and their specifications in the [Cloudflare API documentation](/api/operations/ip-address-management-service-bindings-list-service-bindings).
+:::
+
+## Scope
+
+Currently, if you have BYOIP configured with [Magic Transit](/magic-transit/), you can use the [service binding API](/api/operations/ip-address-management-service-bindings-list-service-bindings) endpoints to add CDN or Spectrum capabilities on top of Magic Transit.
+
+### CDN (Cache)
+
+When you add the CDN service binding, any HTTP requests received via designated IPs are directed into the CDN pipeline (for [Layer 7 processing](/fundamentals/concepts/how-cloudflare-works/#how-cloudflare-works-as-a-reverse-proxy)) as they reach the Cloudflare network.
+
+### Spectrum
+
+Adding [Spectrum](/spectrum/) allows you to benefit from Cloudflare security and performance for Layer 4 traffic.
+
+## Limitations
+
+- It is currently not possible to use both Spectrum and CDN together with the Magic Transit service. You must choose one or the other when upgrading your IPs.
+- You must keep Magic Transit as a common base service, spanning all addresses in your prefix.
+- Once a service binding is created, its propagation across the Cloudflare network will take four to six hours to complete.