dm: ambiguous illustration about WebUI

[buchuitoudegou]

Change Request

This repository is ONLY used to solve problems related to DOCS-CN. For other issues (TiDB, TiKV, etc), please move to other repositories.

Please answer the following questions before submitting your issue. Thanks!

1. Describe what you find is inappropriate or missing in the existing docs.

In the webui doc, it only states that the port to visit WebUI is the same as the one of the OpenAPI. But in fact, we cannot use WebUI unless we turn on the OpenAPI, which should be clearly emphasized in the docs.

related question: https://asktug.com/t/topic/872887

2. Describe your suggestion or addition.

3. Provide some reference materials (documents, websites, etc) if you could.

[buchuitoudegou]

/area dm

[buchuitoudegou]

the prerequisite was removed from this pr: https://github.com/pingcap/docs-cn/pull/9477

[ran-huang]

@WizardXiao PTAL. Do you think we should add the prerequisites?

[buchuitoudegou]

/cc @sunzhaoyang

[Ehco1996]

the openapi feature is turned off by default but webui relies on openapi, so we should add the prerequisites back see https://docs.pingcap.com/zh/tidb/v5.4/dm-open-api cc @ran-huang

[WizardXiao]

@WizardXiao PTAL. Do you think we should add the prerequisites?

agree with @Ehco1996. Open by default will be in other pr.

[ran-huang]

Will do. /assign