Allow users with write permissions for issues to add attachments with API (#26837)

Fixes #24944

Since a user with write permissions for issues can add attachments to an
issue via the the web interface, the user should also be able to add
attachments via the API

routers/api/v1/repo/issue_attachment.go

@@ -344,7 +344,7 @@ func getIssueAttachmentSafeRead(ctx *context.APIContext, issue *issues_model.Iss
 }
 
 func canUserWriteIssueAttachment(ctx *context.APIContext, issue *issues_model.Issue) bool {
-	canEditIssue := ctx.IsSigned && (ctx.Doer.ID == issue.PosterID || ctx.IsUserRepoAdmin() || ctx.IsUserSiteAdmin()) && ctx.Repo.CanWriteIssuesOrPulls(issue.IsPull)
+	canEditIssue := ctx.IsSigned && (ctx.Doer.ID == issue.PosterID || ctx.IsUserRepoAdmin() || ctx.IsUserSiteAdmin() || ctx.Repo.CanWriteIssuesOrPulls(issue.IsPull))
 	if !canEditIssue {
 		ctx.Error(http.StatusForbidden, "", "user should have permission to write issue")
 		return false