feat(mongodb): add full URI and Atlas/SRV support

[Robbyfuu]

Summary

This PR upgrades the existing official MongoDB plugin with full connection URI and MongoDB Atlas support. It does not introduce a parallel plugin: the identity remains mongodb / MongoDB, and the version remains 0.1.0.

Changes

• Accept full mongodb:// and mongodb+srv:// connection URIs.
• Forward full URIs unchanged to the official MongoDB Rust driver, preserving SRV discovery, TLS, multiple hosts, replica-set settings, authentication options, and query parameters.
• Keep legacy host, port, username, password, and database connections compatible.
• Accept database as either a string or an array of selected database names.
• Honor the request-level schema as the active MongoDB database.
• Strip identifier quotes from SQL-like collection browsing queries.
• Redact accepted MongoDB URI forms from driver errors before returning JSON-RPC errors.
• Declare connection_uri support and the mongodb / mongodb+srv schemes in the official manifest.

Host compatibility

Full URI transport requires the host-side passthrough and secure per-connection storage introduced by TabularisDB/tabularis#495. Older Tabularis versions can continue using the legacy host/port fields, but cannot send a complete Atlas/SRV URI to an external plugin.

Scope

The diff is limited to:

• README.md
• manifest.json
• src/main.rs

Registry changes and release publication are intentionally outside this PR.

Validation

• cargo test: 20 passed, 0 failed.
• cargo build --release: passed.
• rustfmt --edition 2021 --check src/main.rs: passed.
• git diff --check: passed.
• Manifest contract: validated official identity, version, executable, nested URI capabilities, exact schemes, and absence of a legacy connection-string example.
• Live Atlas JSON-RPC smoke test: process exited successfully with no stderr; test_connection passed; get_tables returned 16 collections with request-schema propagation; quoted collection browsing returned one row with 15 columns and expected pagination.
• No URI, credentials, request payloads, or document contents were printed during validation.

The repository-wide cargo fmt --check still reports formatting in unchanged upstream src/bin/test.rs; the modified Rust file passes the formatter check above.

[debba]

This looks good for me, feel free to merge when you are ready.