Link method names to API docs [ci-skip]

Note that some of these method names are already linked elsewhere in
their respective guides, hence no need for additional reference URLs.

guides/source/active_record_migrations.md

@@ -548,7 +548,7 @@ While it's not required you might want to add foreign key constraints to
 add_foreign_key :articles, :authors
 ```
 
-This `add_foreign_key` call adds a new constraint to the `articles` table.
+This [`add_foreign_key`][] call adds a new constraint to the `articles` table.
 The constraint guarantees that a row in the `authors` table exists where
 the `id` column matches the `articles.author_id`.
 
@@ -562,8 +562,8 @@ For example, to add a foreign key on `articles.reviewer` referencing `authors.em
 add_foreign_key :articles, :authors, column: :reviewer, primary_key: :email
 ```
 
-Options such as `name`, `on_delete`, `if_not_exists`, `validate`, and `deferrable`
-are described in the [`add_foreign_key`][] API.
+`add_foreign_key` also supports options such as `name`, `on_delete`,
+`if_not_exists`, `validate`, and `deferrable`.
 
 NOTE: Active Record only supports single column foreign keys. `execute` and
 `structure.sql` are required to use composite foreign keys. See
@@ -579,8 +579,6 @@ remove_foreign_key :accounts, :branches
 remove_foreign_key :accounts, column: :owner_id
 ```
 
-[`add_foreign_key`]: https://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/SchemaStatements.html#method-i-add_foreign_key
-
 ### When Helpers aren't Enough
 
 If the helpers provided by Active Record aren't enough you can use the [`execute`][]

guides/source/active_record_querying.md

@@ -1325,7 +1325,7 @@ time_range = (Time.now.midnight - 1.day)..Time.now.midnight
 Customer.joins(:orders).where(orders: { created_at: time_range }).distinct
 ```
 
-For more advanced conditions or to reuse an existing named scope, `Relation#merge` may be used. First, let's add a new named scope to the `Order` model:
+For more advanced conditions or to reuse an existing named scope, [`merge`][] may be used. First, let's add a new named scope to the `Order` model:
 
 ```ruby
 class Order < ApplicationRecord
@@ -1337,7 +1337,7 @@ class Order < ApplicationRecord
 end
 ```
 
-Now we can use `Relation#merge` to merge in the `created_in_time_range` scope:
+Now we can use `merge` to merge in the `created_in_time_range` scope:
 
 ```ruby
 time_range = (Time.now.midnight - 1.day)..Time.now.midnight

guides/source/routing.md

@@ -391,7 +391,7 @@ The articles resource here will have the following routes generated for it:
 | PATCH/PUT | /articles/:id(.:format)                      | articles#update   | article_path             |
 | DELETE    | /articles/:id(.:format)                      | articles#destroy  | article_path             |
 
-The `shallow` method of the DSL creates a scope inside of which every nesting is shallow. This generates the same routes as the previous example:
+The [`shallow`][] method of the DSL creates a scope inside of which every nesting is shallow. This generates the same routes as the previous example:
 
 ```ruby
 shallow do
@@ -447,6 +447,8 @@ The comments resource here will have the following routes generated for it:
 | PATCH/PUT | /comments/:id(.:format)                      | comments#update   | sekret_comment_path         |
 | DELETE    | /comments/:id(.:format)                      | comments#destroy  | sekret_comment_path         |
 
+[`shallow`]: https://api.rubyonrails.org/classes/ActionDispatch/Routing/Mapper/Resources.html#method-i-shallow
+
 ### Routing Concerns
 
 Routing concerns allow you to declare common routes that can be reused inside other resources and routes. To define a concern, use a [`concern`][] block: