/api/entityid doesn't properly process JSON strings

Input data to /api/entityid (and similar endpoints that accept a single string), don't quite make sense me. The endpoint accepts JSON, so I am expected to send a valid JSON data.

However, the schema for that data is just string. So the only valid JSON data I can send is a JSON string (e.g. "abc"). However, if I do so, the entire value I sent is treated as the entity ID (including the quotation marks). I'm, therefore forced to send the string without the quotation marks, which makes my input not valid JSON data, and disagrees with the content type of the request data.

Using text/plain content type causes the server to reject the request.

P.S. I'm not entirely sure this is Mujina's issue, looking at the code, it's all Spring annotations. However, I don't know much about Spring, so may be there is a way to configure this (i.e. it's not a Spring bug).

Start by tracing the Spring annotations and request handling for /api/entityid, then compare the similar endpoints that accept a single string. Reproduce the behavior with a valid JSON string and with text/plain. Done means JSON string input is interpreted as its string value rather than including quotation marks, with the behavior covered for the affected endpoints.