Add Accept header negotiation to relevant API endpoints (#337)

* start centralizing negotiation logic for API

* swagger document nodeinfo endpoint

* go fmt

* document negotiate function

* use content negotiation

* tidy up negotiation logic

* negotiate content throughout client api

* swagger

* remove attachment on Content

* add accept header to test requests

internal/api/s2s/nodeinfo/nodeinfoget.go

@@ -19,20 +19,42 @@
 package nodeinfo
 
 import (
+	"encoding/json"
 	"net/http"
 
 	"github.com/gin-gonic/gin"
 	"github.com/sirupsen/logrus"
+	"github.com/superseriousbusiness/gotosocial/internal/api"
 )
 
-// NodeInfoGETHandler returns a compliant nodeinfo response to node info queries.
-// See: https://nodeinfo.diaspora.software/
+// NodeInfoGETHandler swagger:operation GET /nodeinfo/2.0 nodeInfoGet
+//
+// Returns a compliant nodeinfo response to node info queries.
+//
+// See: https://nodeinfo.diaspora.software/schema.html
+//
+// ---
+// tags:
+// - nodeinfo
+//
+// produces:
+// - application/json; profile="http://nodeinfo.diaspora.software/ns/schema/2.0#"
+//
+// responses:
+//   '200':
+//     schema:
+//       "$ref": "#/definitions/nodeinfo"
 func (m *Module) NodeInfoGETHandler(c *gin.Context) {
 	l := logrus.WithFields(logrus.Fields{
 		"func":       "NodeInfoGETHandler",
 		"user-agent": c.Request.UserAgent(),
 	})
 
+	if _, err := api.NegotiateAccept(c, api.JSONAcceptHeaders...); err != nil {
+		c.JSON(http.StatusNotAcceptable, gin.H{"error": err.Error()})
+		return
+	}
+
 	ni, err := m.processor.GetNodeInfo(c.Request.Context(), c.Request)
 	if err != nil {
 		l.Debugf("error with get node info request: %s", err)
@@ -40,5 +62,10 @@ func (m *Module) NodeInfoGETHandler(c *gin.Context) {
 		return
 	}
 
-	c.JSON(http.StatusOK, ni)
+	b, jsonErr := json.Marshal(ni)
+	if jsonErr != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": jsonErr.Error()})
+	}
+
+	c.Data(http.StatusOK, `application/json; profile="http://nodeinfo.diaspora.software/ns/schema/2.0#"`, b)
 }