Add asset generation from javascript bundle

On `make generate` the `pkg/assets/embed.go` will be generated from the
current state of the javascript app bundle in `assets/accounts.js`. So
you'll have to run `yarn build` first and then `make generate`.

pkg/assets/assets.go

@@ -0,0 +1,36 @@
+package assets
+
+import (
+	"net/http"
+	"os"
+
+	"github.com/owncloud/ocis-accounts/pkg/config"
+	"github.com/owncloud/ocis-pkg/v2/log"
+)
+
+//go:generate go run github.com/UnnoTed/fileb0x embed.yml
+
+// assets gets initialized by New and provides the handler.
+type assets struct {
+	logger log.Logger
+	config *config.Config
+}
+
+// Open just implements the HTTP filesystem interface.
+func (a assets) Open(original string) (http.File, error) {
+	return FS.OpenFile(
+		CTX,
+		original,
+		os.O_RDONLY,
+		0644,
+	)
+}
+
+// New returns a new http filesystem to serve assets.
+func New(opts ...Option) http.FileSystem {
+	options := newOptions(opts...)
+
+	return assets{
+		config: options.Config,
+	}
+}

pkg/assets/embed.yml

@@ -0,0 +1,17 @@
+---
+pkg: "assets"
+dest: "."
+output: "embed.go"
+fmt: true
+noprefix: true
+
+compression:
+  compress: true
+
+custom:
+  - files:
+    - "../../assets/"
+    base: "../../assets/"
+    prefix: ""
+
+...

pkg/assets/option.go

@@ -0,0 +1,40 @@
+package assets
+
+import (
+	"github.com/owncloud/ocis-accounts/pkg/config"
+	"github.com/owncloud/ocis-pkg/v2/log"
+)
+
+// Option defines a single option function.
+type Option func(o *Options)
+
+// Options defines the available options for this package.
+type Options struct {
+	Logger log.Logger
+	Config *config.Config
+}
+
+// newOptions initializes the available default options.
+func newOptions(opts ...Option) Options {
+	opt := Options{}
+
+	for _, o := range opts {
+		o(&opt)
+	}
+
+	return opt
+}
+
+// Logger provides a function to set the logger option.
+func Logger(val log.Logger) Option {
+	return func(o *Options) {
+		o.Logger = val
+	}
+}
+
+// Config provides a function to set the config option.
+func Config(val *config.Config) Option {
+	return func(o *Options) {
+		o.Config = val
+	}
+}