[DOCS] Explain possible values for IDP EntityID (elastic/x-pack-elasticsearch#3875)
Resolves elastic/x-pack-elasticsearch#3865
Original commit: elastic/x-pack-elasticsearch@4c4396b328ef1f738c49f5af2b9840c67e32ce9f
@@ -36,7 +36,11 @@ for SAML realms.
| `enabled` | no | Indicates whether this realm is enabled or disabled. Enables
you to disable a realm without removing its configuration.
Defaults to `true`.
-| `idp.entity_id` | yes | The Entity ID of the SAML Identity Provider
+| `idp.entity_id` | yes | The Entity ID of the SAML Identity Provider. An Entity ID is
+ a URI with a maximum length of 1024 characters. It can be a
+ URL (`https://idp.example.com/`) or a URN (`urn:example.com:idp`)
+ and can be found in the configuration or the SAML metadata
+ of the Identity Provider.
| `idp.metadata.path` | yes | The path (_recommended_) or URL to a SAML 2.0 metadata file
describing the capabilities and configuration of the Identity
Provider.
