Simplify Go Endpoints + Add Tests (#120)

This MR represents a major refactor of the Go codebase, as well as introducing tests for the handlers. The MR also introduces an endpoint to shutdown or restart the Go server, which may be useful for clients who want to refresh the state of the plugin after checking out branches. Finally, this MR adds a contributing document for users who want to make feature changes.

cmd/summary.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"net/http"
+
+	"github.com/xanzy/go-gitlab"
+)
+
+type SummaryUpdateRequest struct {
+	Description string `json:"description"`
+	Title       string `json:"title"`
+}
+
+type SummaryUpdateResponse struct {
+	SuccessResponse
+	MergeRequest *gitlab.MergeRequest `json:"mr"`
+}
+
+func (a *api) summaryHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json")
+
+	if r.Method != http.MethodPut {
+		w.Header().Set("Access-Control-Allow-Methods", http.MethodPut)
+		handleError(w, InvalidRequestError{}, "Expected PUT", http.StatusMethodNotAllowed)
+		return
+	}
+
+	body, err := io.ReadAll(r.Body)
+	if err != nil {
+		handleError(w, err, "Could not read request body", http.StatusBadRequest)
+		return
+	}
+
+	defer r.Body.Close()
+	var SummaryUpdateRequest SummaryUpdateRequest
+	err = json.Unmarshal(body, &SummaryUpdateRequest)
+
+	if err != nil {
+		handleError(w, err, "Could not read JSON from request", http.StatusBadRequest)
+		return
+	}
+
+	mr, res, err := a.client.UpdateMergeRequest(a.projectInfo.ProjectId, a.projectInfo.MergeId, &gitlab.UpdateMergeRequestOptions{
+		Description: &SummaryUpdateRequest.Description,
+		Title:       &SummaryUpdateRequest.Title,
+	})
+
+	if err != nil {
+		handleError(w, err, "Could not edit merge request summary", http.StatusInternalServerError)
+		return
+	}
+
+	if res.StatusCode >= 300 {
+		handleError(w, GenericError{endpoint: "/summary"}, "Could not edit merge request summary", res.StatusCode)
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+
+	response := SummaryUpdateResponse{
+		SuccessResponse: SuccessResponse{
+			Message: "Summary updated",
+			Status:  http.StatusOK,
+		},
+		MergeRequest: mr,
+	}
+
+	err = json.NewEncoder(w).Encode(response)
+	if err != nil {
+		handleError(w, err, "Could not encode response", http.StatusInternalServerError)
+	}
+
+}