This commit updates the topic links obtained from clicking
the topics in the left sidebar, recent view and inbox, and
those obtained from "Copy link to topic" to use the new
topic permalinks.
Fixes part of #21505.
This commit is a part of the work to support empty
string as a topic name.
Previously, empty string was not a valid topic name.
Adds `allow_empty_topic_name` boolean parameter to
`GET /users/me/{stream_id}/topics` endpoint to decide
whether the topic names in the fetched `topics` array
can be empty strings.
If False, the topic names in the fetched response will
have the value of `realm_empty_topic_display_name` field
in `POST /register` response replacing "".
Fixes part of #23291.
This commit adds `allow_empty_name: true` to the following
endpoints to receive empty strings as topic name when such
topics are available:
* `GET /messages`
* `GET /messages/{message_id}`
* `GET /messages/{message_id}/history`
Also, it adds `empty_topic_name` client capability for spectators.
These changes are part of the broader effort to enable
support for empty string as a topic name.
Since we allow calling `add_messages` without checking fetch status,
it can lead to non-contiguous message history due to latest message
being added to a message list without previous messages being
fetched.
To fix it, we only allow adding new messages via message_fetch
which properly sets `anchor` to the last message in the list
before fetching and adding messages to the list.
