Adds the migration, queries, generated code, dbauthz wrappers, and
dbcrypt interceptors for two new columns on mcp_server_configs:
- custom_headers_user_keys: list of keys the user must supply
- custom_headers_user_key_descriptions: optional per-key blurbs
This is the database foundation for a follow-up MCP user-headers
feature. The minimal struct-literal updates in coderd/mcp.go keep
the existing handlers compiling under exhaustruct after the new
fields are added to InsertMCPServerConfigParams and
UpdateMCPServerConfigParams; the handlers do not yet manage the
new fields, which lands in a later stack PR.
Stack: 1/6 (db foundation)
Steven Masley
6d2811f6f8