Jira API - Set Assignee and Apply Transition in 1 Call - jira

Question

Is it possible to set an assignee and apply a transition (change status) in a single call to the Jira Cloud REST API? The example from the documentation here seems to imply that you can, but it does not work when I tested it.
Here's some examples (with curl):
setting an assignee works
curl --request PUT \
--url "https://mysite.atlassian.net/rest/api/2/issue/project-123" \
--user "johnsmith#example.com:abcdef1234567890abcdef00" \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '{
"fields": {
"assignee": { "accountId": "987654321fedcba987654321" }
}
}'
applying a transition works too
curl --request POST \
--url "https://mysite.atlassian.net/rest/api/2/issue/project-123/transitions" \
--user "johnsmith#example.com:abcdef1234567890abcdef00" \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '{
"transition": { "id": 1 }
}'
error saying that assignee cannot be set
curl --request POST \
--url "https://mysite.atlassian.net/rest/api/2/issue/project-123/transitions" \
--user "johnsmith#example.com:abcdef1234567890abcdef00" \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '{
"fields": {
"assignee": {
"accountId": "987654321fedcba987654321"
}
},
"transition": {
"id": 1
}
}'
sets assignee, but doesn't apply transition
curl --request PUT \
--url "https://mysite.atlassian.net/rest/api/2/issue/project-123" \
--user "johnsmith#example.com:abcdef1234567890abcdef00" \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '{
"fields": {
"assignee": {
"accountId": "987654321fedcba987654321"
}
},
"transition": {
"id": 1
}
}'

Answer 1

you cannot do that in one request because you're sending them to two different URLs.

Answer 2

On JIRA Server 8.7.1, was able to successfully transition using the name property (instead of accountId).
curl --request POST \
--url "https://mysite.atlassian.net/rest/api/2/issue/project-123/transitions" \
--user "johnsmith#example.com:abcdef1234567890abcdef00" \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--data '{
"fields": {
"assignee": {
"name": "will"
}
},
"transition": {
"id": 1
}
}'
Otherwise I got the following error:
{
"errorMessages": [],
"errors": {
"assignee": "expected Object containing a 'name' property"
}
}