Fix MONGOID-5006 Link default auth source documentation to driver instead of incorrectly claiming "admin" is always the default

docs/reference/configuration.txt

@@ -139,7 +139,7 @@ can be configured.
           - myhost3.mydomain.com:27017
         options:
           # These options are Ruby driver options, documented in
-          # https://docs.mongodb.com/ruby-driver/current/tutorials/ruby-driver-create-client/
+          # https://docs.mongodb.com/ruby-driver/current/reference/create-client/
 
           # Change the default write concern. (default = { w: 1 })
           write:
@@ -168,7 +168,13 @@ can be configured.
           # on 2.4 and 2.6 is :plain)
           auth_mech: :scram
 
-          # The database or source to authenticate the user against. (default: admin)
+          # Specify the auth source, i.e. the database or other source which
+          # contains the user's login credentials. Allowed values for auth source
+          # depend on the authentication mechanism, as explained in the server documentation:
+          # https://docs.mongodb.com/manual/reference/connection-string/#mongodb-urioption-urioption.authSource
+          # If no auth source is specified, the default auth source as
+          # determined by the driver will be used. Please refer to:
+          # https://docs.mongodb.com/ruby-driver/current/reference/authentication/#auth-source
           auth_source: admin
 
           # Force the driver to connect in a specific way instead of auto-
@@ -291,7 +297,7 @@ can be configured.
       use_utc: false
 
 The Ruby driver options may be found in
-`the driver documentation <https://docs.mongodb.com/ruby-driver/current/tutorials/ruby-driver-create-client/>`_.
+`the driver documentation <https://docs.mongodb.com/ruby-driver/current/reference/create-client/>`_.
 
 ERb Preprocessing
 =================
@@ -596,7 +602,7 @@ be executed sequentially during socket creation.
   in an application.
 
 For more information about TLS context hooks, including best practices for
-assigning and removing them, see `the Ruby driver documentation <https://docs.mongodb.com/ruby-driver/current/tutorials/ruby-driver-create-client/#modifying-sslcontext>`_.
+assigning and removing them, see `the Ruby driver documentation <https://docs.mongodb.com/ruby-driver/current/reference/create-client/#modifying-sslcontext>`_.
 
 Usage with Forking Servers
 ==========================

docs/reference/queries.txt

@@ -1107,7 +1107,7 @@ the query cache. When using driver versions 2.14.0 or newer, this interface
 will affect the driver query cache.
 
 Read more about the Ruby driver query cache
-`in the driver documentation <https://docs.mongodb.com/ruby-driver/current/tutorials/query-cache/>`_.
+`in the driver documentation <https://docs.mongodb.com/ruby-driver/current/reference/query-cache/>`_.
 
 .. warning::
 
@@ -1118,7 +1118,7 @@ Read more about the Ruby driver query cache
   recommended that you upgrade to Ruby driver version 2.14.0 or newer.
 
   Read more about the Ruby driver query cache
-  `in the driver documentation <https://docs.mongodb.com/ruby-driver/current/tutorials/query-cache/>`_.
+  `in the driver documentation <https://docs.mongodb.com/ruby-driver/current/reference/query-cache/>`_.
 
 Legacy Query Cache Limitations
 ------------------------------

docs/release-notes/mongoid-7.2.txt

@@ -402,7 +402,7 @@ Mongoid query cache. If you plan to use the query cache, it is recommended
 that you upgrade to driver version 2.14.
 
 To read more about the query cache improvements made in the driver, see
-`the Ruby driver documentation <https://docs.mongodb.com/ruby-driver/current/tutorials/query-cache/>`_.
+`the Ruby driver documentation <https://docs.mongodb.com/ruby-driver/current/reference/query-cache/>`_.
 
 To read more about using the query cache with Mongoid and the limitations
 of the legacy query cache, see :ref:`the query cache documentation <query-cache>`.