I see occasional confusion about the explanations emitted by the same-shard
allocation decider, particularly amongst new users setting up a single-node
cluster and trying to determine why their cluster has `yellow` health. For
example:
the shard cannot be allocated to the same node on which a copy of the shard
already exists
This is technically correct but it's quite a complicated sentence. Also, by
starting with "the shard cannot be allocated" it makes it sound like this is
the problem, whereas in fact this message is a good thing and users should
typically focus their attention elsewhere.
This commit simplifies the wording of these messages and makes them sound more
positive, for example:
a copy of this shard is already allocated to this node
69f50fe79f