Adds three experimental endpoints under /api/experimental/mcp/servers/
{mcpServer}/user-headers that let a user manage their own values for
the admin-marked custom_headers_user_keys on an MCP server.
- GET returns an MCPServerUserHeaderValues with a HasValues map keyed
by every admin-marked user key. Values are never returned, only
booleans indicating whether the caller has stored a non-empty value.
- PUT upserts a subset of values. Unknown keys are rejected with 400.
Keys are matched case-insensitively but stored under the admin's
canonical casing. A partial PUT preserves existing values for keys
the request did not touch; sending an empty string clears a single
value.
- DELETE removes the row entirely and is idempotent.
The Upsert dbauthz wrapper switches to insertWithAction so the first
write does not require a pre-existing row.
Steven Masley
33d7bf1760