added missing group subject field

doc/api.oa3

@@ -878,6 +878,46 @@ paths:
             schema:
               $ref: '#/components/schemas/Subject'
          
+  /alias/groups/{groupId}/subject/{field}:
+    get:
+      tags:
+        - alias
+      description: Base64 decode and download specified field from the groups's subject. Access granted to app token of account holder.
+      operationId: get-group-subject-field
+      security:
+        - bearerAuth: []
+      parameters:
+        - name: groupId
+          in: path
+          description: specified group id
+          required: true
+          schema:
+            type: string
+        - name: field
+          in: path
+          description: field from subject to base64 decode and download
+          required: true
+          schema:
+            type: string
+      responses:
+        '200':
+          description: success
+          content:
+            application/json:
+              schema:
+                type: string
+                format: binary
+        '401':
+          description: permission denied
+        '404':
+          description: field, article not found
+        '405':
+          description: invalid field
+        '410':
+          description: account disabled
+        '500':
+          description: internal server error
+ 
   /alias/groups/{groupId}/subject:
     put:
       tags:

net/server/internal/api_getGroupSubjectField.go

@@ -0,0 +1,56 @@
+package databag
+
+import (
+  "time"
+  "bytes"
+  "errors"
+  "strings"
+  "net/http"
+  "gorm.io/gorm"
+  "encoding/base64"
+  "github.com/gorilla/mux"
+  "databag/internal/store"
+  "github.com/valyala/fastjson"
+)
+
+func GetGroupSubjectField(w http.ResponseWriter, r *http.Request) {
+
+  // scan parameters
+  params := mux.Vars(r)
+  groupId := params["groupId"]
+  field := params["field"]
+  elements := strings.Split(field, ".")
+
+  account, code, err := BearerAppToken(r, false);
+  if err != nil {
+    ErrResponse(w, code, err)
+    return
+  }
+
+  // load group
+  var slot store.GroupSlot
+  if err := store.DB.Preload("Group.GroupData").Where("account_id = ? AND group_slot_id = ?", account.ID, groupId).First(&slot).Error; err != nil {
+    if errors.Is(err, gorm.ErrRecordNotFound) {
+      ErrResponse(w, http.StatusNotFound, err)
+    } else {
+      ErrResponse(w, http.StatusInternalServerError, err)
+    }
+    return
+  }
+  if slot.Group == nil {
+    ErrResponse(w, http.StatusNotFound, errors.New("referenced group missing"))
+    return
+  }
+
+  // decode data
+  strData := fastjson.GetString([]byte(slot.Group.GroupData.Data), elements...)
+  binData, err := base64.StdEncoding.DecodeString(strData)
+  if err != nil {
+    ErrResponse(w, http.StatusNotFound, err)
+    return
+  }
+
+  // response with content
+  http.ServeContent(w, r, field, time.Unix(slot.Group.Updated, 0), bytes.NewReader(binData))
+}
+

net/server/internal/routers.go

@@ -271,6 +271,13 @@ var routes = Routes{
 		AddGroup,
 	},
 
+	Route{
+		"GetGroupSubjectField",
+		strings.ToUpper("Get"),
+		"/alias/groups/{groupId}/subject/{field}",
+		GetGroupSubjectField,
+	},
+
 	Route{
 		"GetGroups",
 		strings.ToUpper("Get"),