docs: mention service name restrictions in publish docs (#6590)

Co-authored-by: Laurin Quast <[email protected]>

Author: jdolle

packages/web/docs/src/content/schema-registry/index.mdx

@@ -130,7 +130,8 @@ Here's an overview of what each of these steps means:
   schema. You can include any information you wish to include in this JSON object (see
   [Publishing Hive metadata](/docs/api-reference/cli#hive-metadata)).
 - **Service Name**: the name of the service. This is used for Schema-Stitching and Apollo Federation
-  only.
+  only. A service name is restricted to 64 characters, must start with a letter, and can only
+  contain alphanumeric, `-`, and `_` characters.
 - **Service URL**: the URL of the service. This is used for Schema-Stitching and Apollo Federation
   only.