Improve Codebase :: Contract Drift

[81reap]

I have started on this path with #1382 but I thought it would be worth creating an issue to track all of the changes I'm thinking about that will come after this. This audit was done with the help of Claude.

B1. configuration.md — six defaults are wrong or incomplete

Option	Documented	Actual	Reference
system_root_ca_certificates	false	true whenever SSL_CERT_FILE or SSL_CERT_DIR is set	app_config.rs:729-732
listen_on / port	0.0.0.0:8080 / 8080	443 when https_domain is set	app_config.rs:426-436
database_url	sqlite://sqlpage.db?mode=rwc	path is relative to the configuration directory; falls back to in-memory if that is not writable; a legacy ./sqlpage.db wins if present	app_config.rs:630-673
max_database_pool_connections	4 backends listed	5 branches — ODBC is 50 and in-memory SQLite is 128, neither documented	connect.rs:82-95
https_certificate_cache_dir	./sqlpage/https	derived from the process working directory, not from the configured web_root or configuration directory	app_config.rs:711-713
max_recursion_depth	"Maximum value is 255"	not a cap — the u8 type makes 256 a startup failure	app_config.rs:405-406

Also drifted inside the code. The Rust doc comment at app_config.rs:290 says the default upload limit is 10 MiB. The actual default at :703-705 is 5 MiB, and configuration.md correctly says 5 MiB.

Suggested fix. Correct the rows. Then, optionally, add a test that parses the (stable, three-column) table and asserts that documented option names match the struct's serde names and that documented defaults match the values produced by deserialising {}.

B2. sqlpage.request_body() returns '' where the documentation says NULL

What happens. examples/official-site/sqlpage/migrations/55_request_body.sql:65 says the function "returns NULL if there is no request body". On a request with no body SQLPage actually returns an empty string.

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B3. fetch_with_meta emits a json_body key that its documentation does not mention

What happens. sqlpage.fetch_with_meta returns the response body under the key body for text responses and under json_body for JSON responses. The documentation
(examples/official-site/sqlpage/migrations/58_fetch_with_meta.sql:14-23) documents a single body key holding "a string, or a json object, depending on the content type".