The Power BI REST API lives at https://api.powerbi.com/v1.0/myorg. Workspaces are called groups.
Power BI uses Microsoft Entra ID tokens for the https://analysis.windows.net/powerbi/api resource. For testing, the REST API docs' Try It panel signs you in. Send the token as Authorization: Bearer <token>, written {{POWERBI_TOKEN}}.
Full reference: https://learn.microsoft.com/en-us/rest/api/power-bi/
curl https://api.powerbi.com/v1.0/myorg/groups \
-H "Authorization: Bearer {{POWERBI_TOKEN}}"
curl https://api.powerbi.com/v1.0/myorg/groups/{{GROUP_ID}}/reports \
-H "Authorization: Bearer {{POWERBI_TOKEN}}"
curl -X POST https://api.powerbi.com/v1.0/myorg/groups/{{GROUP_ID}}/datasets/{{DATASET_ID}}/refreshes \
-H "Authorization: Bearer {{POWERBI_TOKEN}}" \
-H "Content-Type: application/json" \
-d '{"notifyOption": "NoNotification"}'