Improve docs

lib/ecto.ex

@@ -637,6 +637,16 @@ defmodule Ecto do
     Ecto.Schema.Loader.unsafe_load(schema_or_types, data, &Ecto.Type.embedded_load(&1, &2, format))
   end
 
+  @doc """
+  Dumps the given struct defined by an embedded schema.
+
+  This converts the given embedded schema to a map to be serialized
+  with the given format. For example:
+
+      iex> Ecto.embedded_dump(%Post{}, :json)
+      %{title: "hello"}
+
+  """
   @spec embedded_dump(Ecto.Schema.t(), format :: atom()) :: map()
   def embedded_dump(%schema{} = data, format) do
     Ecto.Schema.Loader.safe_dump(data, schema.__schema__(:dump), &Ecto.Type.embedded_dump(&1, &2, format))

lib/ecto/repo.ex

@@ -92,7 +92,20 @@ defmodule Ecto.Repo do
     * `:telemetry_options` - Extra options to attach to telemetry event name.
       See the next section for more information
 
-  ### Telemetry events
+  ## Telemetry events
+
+  There are two types of telemetry events. The ones emitted by Ecto and the
+  ones that are adapter specific.
+
+  ### Ecto telemetry events
+
+  The following events are emitted by all Ecto repositories:
+
+    * `[:ecto, :repo, :init]` - it is invoked whenever a repository starts.
+      The measurement is a single `system_time` entry in native unit. The
+      metadata is the `:repo` and all initialization options under `:opts`.
+
+  ### Adapter-specific events
 
   We recommend adapters to publish certain `Telemetry` events listed below.
   Those events will use the `:telemetry_prefix` outlined above which defaults