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/user.go

@@ -0,0 +1,27 @@
+package gitea
+
+import "time"
+
+type User struct {
+	Id                  uint
+	Login               string
+	Login_name          string
+	Full_name           string
+	Email               string
+	Avatar_url          string
+	Language            string
+	Is_admin            bool
+	Last_login          time.Time
+	Created             time.Time
+	Restricted          bool
+	Active              bool
+	Prohibit_login      bool
+	Location            string
+	Website             string
+	Description         string
+	Visibility          string
+	Followers_count     uint
+	Following_count     uint
+	Starred_repos_count uint
+	Username            string
+}