Do more type checking when setting HS idents.

I repurposed the old directory_request_set_hs_ident() into a new
directory_request_upload_set_hs_ident() which is only used for the
upload purpose and so it can assert on the dir_purpose.

When coding the client-side we can make a second function for fetch.

src/or/directory.c

@@ -1281,12 +1281,11 @@ directory_request_set_rend_query(directory_request_t *req,
  * <b>ident</b> object must outlive the request.
  */
 void
-directory_request_set_hs_ident(directory_request_t *req,
-                               const hs_ident_dir_conn_t *ident)
+directory_request_upload_set_hs_ident(directory_request_t *req,
+                                      const hs_ident_dir_conn_t *ident)
 {
   if (ident) {
-    tor_assert(req->dir_purpose == DIR_PURPOSE_FETCH_HSDESC ||
-               req->dir_purpose == DIR_PURPOSE_UPLOAD_HSDESC);
+    tor_assert(req->dir_purpose == DIR_PURPOSE_UPLOAD_HSDESC);
   }
   req->hs_ident = ident;
 }

src/or/directory.h

@@ -73,8 +73,8 @@ void directory_request_set_if_modified_since(directory_request_t *req,
                                              time_t if_modified_since);
 void directory_request_set_rend_query(directory_request_t *req,
                                       const rend_data_t *query);
-void directory_request_set_hs_ident(directory_request_t *req,
-                                    const hs_ident_dir_conn_t *ident);
+void directory_request_upload_set_hs_ident(directory_request_t *req,
+                                           const hs_ident_dir_conn_t *ident);
 
 void directory_request_set_routerstatus(directory_request_t *req,
                                         const routerstatus_t *rs);

src/or/hs_service.c

@@ -1957,7 +1957,7 @@ upload_descriptor_to_hsdir(const hs_service_t *service,
                                 strlen(encoded_desc));
   /* The ident object is copied over the directory connection object once
    * the directory request is initiated. */
-  directory_request_set_hs_ident(dir_req, &ident);
+  directory_request_upload_set_hs_ident(dir_req, &ident);
 
   /* Initiate the directory request to the hsdir.*/
   directory_initiate_request(dir_req);