Fix set_issue_fields mutation: use correct inline fragments for IssueFieldValue union

The mutation response struct used a single inline fragment
'... on IssueFieldDateValue' with a 'Name' field that doesn't exist
on that type (only IssueFieldSingleSelectValue has 'name'). This
caused GraphQL validation to fail with:

  Field 'name' doesn't exist on type 'IssueFieldDateValue'

Since GraphQL validates the entire document (including response
selection sets) before executing any operation, the mutation never
fired at all — no fields were ever set regardless of input.

Fix by adding correct inline fragments for all four union types:
- IssueFieldTextValue (value)
- IssueFieldSingleSelectValue (name)
- IssueFieldDateValue (value)
- IssueFieldNumberValue (value)

Author: iulia-b

pkg/github/issues_granular.go

@@ -793,9 +793,18 @@ func GranularSetIssueFields(t translations.TranslationHelperFunc) inventory.Serv
 						URL    githubv4.String
 					}
 					IssueFieldValues []struct {
-						Field struct {
+						TextValue struct {
+							Value string
+						} `graphql:"... on IssueFieldTextValue"`
+						SingleSelectValue struct {
 							Name string
+						} `graphql:"... on IssueFieldSingleSelectValue"`
+						DateValue struct {
+							Value string
 						} `graphql:"... on IssueFieldDateValue"`
+						NumberValue struct {
+							Value float64
+						} `graphql:"... on IssueFieldNumberValue"`
 					}
 				} `graphql:"setIssueFieldValue(input: $input)"`
 			}