anchor.diff:    "full_name": "Service account - elastic/fleet-server",
     "email": null,
     "token": {
  -    "name": "token1"      <1>
  +    "name": "token1",                 <1>
  +    "type": "_service_account_index"  <2>
     },
     "metadata": {
       "_elastic_service_account": true
     },
     "enabled": true,
     "authentication_realm": {
  -    "name": "service_account",
  -    "type": "service_account"
  +    "name": "_service_account",
  +    "type": "_service_account"
     },
     "lookup_realm": {
  -    "name": "service_account",
  -    "type": "service_account"
  +    "name": "_service_account",
  +    "type": "_service_account"
     },
     "authentication_type": "token"
   }
   ----
   // NOTCONSOLE
  -<1> Name of the service account token
  +<1> Name of the service account token.
  +<2> Type of service account token. The value always begins with
  +`_service_account_` and is followed by a string that indicates the service
  +token backend in use (can be either `file` or `index`).
  
positive.code: interface. See <<encrypt-http-communication,encrypt HTTP client communications for {es}>>.
  // end::service-accounts-tls[]
  
  [[service-accounts-tokens]]
  ==== How service account tokens work
  A service account token, or simply service token,
  is a unique string that a service uses to authenticate
  with {es}. For a given service account, each token must have a unique name.
  Because tokens include access credentials, they should always be kept secret
  by whichever client is using them.
  
  Service account tokens can be backed by either the `service_tokens` file or the
  `.security` index. You can create multiple service account tokens for a single
  service account, which enables multiple instances of the same service to run
  with different credentials.
  
  You must create a service account token to use a service account. You can
  create a service account token using either:
  
  * The <<service-tokens-command,elasticsearch-service-tokens>> CLI tool, which
  saves the new service account token in the `$ES_HOME/config/service_tokens` file
  and outputs the bearer token to your terminal
  * The <<security-api-create-service-token,create service account tokens API>>,
  which saves the new service account token in the `.security` index and returns
  the bearer token in the HTTP response
  
  Service account tokens never expire. You must actively <<security-api-delete-service-token,delete>> them if they are no longer needed.
  
  [[authenticate-with-service-account-token]]
  ==== Authenticate with service account tokens
  
  NOTE: Service accounts currently do not support basic authentication.
  
  
negative.code: 
  The {stack-security-features} provide _service accounts_ specifically for
  integration with external services that connect to {es}, such as {fleet} server.
  Service accounts have a fixed set of privileges and cannot authenticate
  until you create a service account token for them. Additionally, service
  accounts are predefined in code, and are always enabled.
  
  A service account corresponds to a specific external service. You create service
  account tokens for a service account. The service can then authenticate with the
  token and perform relevant actions. For example, {fleet} server can use its
  service token to authenticate with {es} and then manage its own API keys.
  
  You can create multiple service tokens for the same service account, which
  prevents credential sharing between multiple instances of the same
  external service. Each instance can assume the same identity while using
  their own distinct service token for authentication.
  
  Service accounts provide flexibility over <<built-in-users,built-in users>> 
  because they:
  
  * Do not rely on the <<native-realm,internal `native` realm>>, and aren't
  always required to rely on the `.security` index
  * Use a role descriptor named after the service account principal instead of 
  traditional roles
  * Support multiple credentials through service account tokens
  
  Service accounts are not included in the response of the
  <<security-api-get-user,get users API>>. To retrieve a service account, use the
  <<security-api-get-service-accounts,get service accounts API>>.
  
  [discrete]
  [[service-accounts-explanation]]
  === Service accounts usage
  Service accounts have a
  <<security-api-get-service-accounts-path-params,unique principal>> that takes
  the format of `<namespace>/<service>`, where the `namespace` is a top-level
  grouping of service accounts, and `service` is the name of the service and
  must be unique within its namespace.
  
  Service accounts are predefined in code. Currently, only one service account is available:
  
  `elastic/fleet-server`:: The service account used by the {fleet} server to
  communicate with {es}.
  
  // tag::service-accounts-usage[]
  IMPORTANT: Do not attempt to use service accounts for authenticating individual
  users. Service accounts can only be authenticated with service tokens, which are
  not applicable to regular users.
  // end::service-accounts-usage[]
  
  // tag::service-accounts-tls[]
  