App Identity for Elixir Changelog

1.4.0 / 2023-MM-DD

Made mix app_identity help more robust so that it works when not provided an additional command, printing the same content as mix help app_identity.

Resolved an issue where padlock values sent using lowercase hex values were not comparing properly. Added tests for the case as well as an additional validation doctest.

Packages released to hex.pm by default include the priv/ directory, but nothing is done to ensure that those packages include anything other than the literal files. The priv/ directory contained two symbolic links (optional.json and required.json) which were symlinks to the project integration suite generators, only used in integration testing.

Rename many spec uses of String.t() to binary() as we do not necessarily require UTF-8.
Extensive reorganization of the AppIdentity.Plug documentation to improve the readability of the configuration.
Refactored configuration into AppIdentity.Plug.Config from the plug itself. This was done in part to resolve a Dialyzer issue.
Add on_resolution and on_success callbacks in AppIdentity.Plug.Config to better support various workflows (such as adding proof validation results to Logger.metadata/1).
Extended the AppIdentity.Plug.Config.finder callback to accept a tuple {module, function}.
Improved AppIdentity.Plug.Config telemetry context formatting to include the plug name.

Add support for header groups in AppIdentity.Plug to better handle fallback headers. Kinetic’s original Elixir implementation always verified only the first value from a list of headers, like so:
```
with [] <- Conn.get_req_header(conn, "header-1"),
     [] <- Conn.get_req_header(conn, "header-2"),
     [] <- Conn.get_req_header(conn, "header-3") do
  :error
else
  [value | _] -> {:ok, value}
end
```
AppIdentity.Plug always processes all values of a header and puts the result in a map with the header name as the key, it meant that each header result would need to be checked individually. Instead, the header_groups option collects related headers into a single result key:
```
plug AppIdentity.Plug, header_groups: %{
  "app" => ["header-1", "header-2", "header-3"]
}, ...
```
Add support for alternate names so that AppIdentity.Plug can be specified multiple times in a pipeline and will store its data separately.