doi: add new doi backend

Add a new backend to support mounting datasets published with a digital
object identifier (DOI).

backend/doi/link_header_internal_test.go

@@ -0,0 +1,44 @@
+package doi
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseLinkHeader(t *testing.T) {
+	header := "<https://zenodo.org/api/records/15063252> ; rel=\"linkset\" ; type=\"application/linkset+json\""
+	links := parseLinkHeader(header)
+	expected := headerLink{
+		Href:   "https://zenodo.org/api/records/15063252",
+		Rel:    "linkset",
+		Type:   "application/linkset+json",
+		Extras: map[string]string{},
+	}
+	assert.Contains(t, links, expected)
+
+	header = "<https://api.example.com/issues?page=2>; rel=\"prev\", <https://api.example.com/issues?page=4>; rel=\"next\", <https://api.example.com/issues?page=10>; rel=\"last\", <https://api.example.com/issues?page=1>; rel=\"first\""
+	links = parseLinkHeader(header)
+	expectedList := []headerLink{{
+		Href:   "https://api.example.com/issues?page=2",
+		Rel:    "prev",
+		Type:   "",
+		Extras: map[string]string{},
+	}, {
+		Href:   "https://api.example.com/issues?page=4",
+		Rel:    "next",
+		Type:   "",
+		Extras: map[string]string{},
+	}, {
+		Href:   "https://api.example.com/issues?page=10",
+		Rel:    "last",
+		Type:   "",
+		Extras: map[string]string{},
+	}, {
+		Href:   "https://api.example.com/issues?page=1",
+		Rel:    "first",
+		Type:   "",
+		Extras: map[string]string{},
+	}}
+	assert.Equal(t, links, expectedList)
+}