add(gitea-api): issues and milestones getters

This implements the api getters for extracting the issues and milestones
for a given gitea repository. WIP for #1.

internal/gitea/milestone.go

@@ -1 +1,38 @@
 package gitea
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+)
+
+type Milestone struct {
+	Id            uint
+	Title         string
+	Description   string
+	State         string
+	Open_issues   uint
+	Closed_issues uint
+	Created_at    time.Time
+	Updated_at    time.Time
+	Due_on        time.Time
+	Closed_at     time.Time
+}
+
+func (gitea *Gitea) GetMilestones(repo Repository) ([]Milestone, error) {
+	url := fmt.Sprintf("%s/repos/%s/milestones?state=all", gitea.Url(), repo.Full_name)
+	response, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer response.Body.Close()
+	var data []Milestone
+	decoder := json.NewDecoder(response.Body)
+	// NOTE: remove this if I do not want to store everything from the json result in the struct
+	decoder.DisallowUnknownFields() // remain if every field shall be extracted
+	if err = decoder.Decode(&data); err != nil {
+		return nil, err
+	}
+	return data, nil
+}