sensitive configuration options should be only write only

configuration options containing passwords should be write only:

• redcap API token
• NEXMO_API_KEY
• NEXMO API_SECRET

changed milestone to %1.0.0

added enhancement label

mentioned in merge request !271 (merged)

created merge request !280 (merged) to address this issue

mentioned in merge request !280 (merged)

assigned to @piotr.gawron

closed with merge request !280 (merged)

mentioned in commit 1f530b23