### Description

Dynamic mappings can greatly help the getting started experience but they currently don't apply to all types, one example is `dense_vector`.

It's been suggested to automatically map float arrays as dense vectors when there are more than 100 values, or a heuristic along these lines.
server/src/internalClusterTest/java/org/elasticsearch/index/mapper/DynamicMappingIT.java
);
                    } catch (Exception e) {
                        error.compareAndSet(null, e);
                    }
                }
            });
            indexThreads[i].start();
        }
        startLatch.countDown();
        for (Thread thread : indexThreads) {
            thread.join();
        }
        if (error.get() != null) {
            throw error.get();
        }
        Thread.sleep(2000);
        GetMappingsResponse mappings = indicesAdmin().prepareGetMappings("index").get();
        for (int i = 0; i < indexThreads.length; ++i) {
            assertMappingsHaveField(mappings, "index", "field" + i);
        }
        for (int i = 0; i < indexThreads.length; ++i) {
            assertTrue(client().prepareGet("index", Integer.toString(i)).get().isExists());
        }
    }
    public void testPreflightCheckAvoidsMaster() throws InterruptedException, IOException {
        
        
        createIndex("index", Settings.builder().put(INDEX_MAPPING_NESTED_FIELDS_LIMIT_SETTING.getKey(), 2).build());
        ensureGreen("index");
        indicesAdmin().preparePutMapping("index")