feat(connections): allow database override via "<id>/<database>" syntax

[rrsela]

Summary

Adds support for a <connectionId>/<database> override syntax on every tool that takes a connectionId, so a single workspace connection can target any database on the same server — no need to create N workspace connections for an N-database cluster.

Why

PostgreSQL (and other) connections are bound to a single database (the one in the JDBC URL / workspace config). When you browse a multi-DB server in DBeaver's navigator, DBeaver transparently opens additional sessions per database under the hood. The MCP server doesn't replicate that — it builds one client per logical workspace connection — so to query 8 databases on a cluster, you currently have to define 8 separate workspace connections.

This is impractical when:

• A cluster has many tenant DBs (one DB per service)
• You want to script lookups across DBs ad-hoc
• You don't control the workspace config

What changed

• src/utils.ts: extend sanitizeConnectionId to preserve /; add a small parseConnectionId helper that splits <id>/<database> into { baseId, databaseOverride }.
• src/config-parser.ts: getConnection consumes parseConnectionId, looks up by baseId as before, and when an override is present returns a shallow clone with:
  • id = ${match.id}/${databaseOverride} (so per-DB pool caches stay separate)
  • database = override
  • properties.database = override
  • all other fields (host/port/user/password/SSL config) preserved
• The original cached connection object is not mutated.

Backwards compatibility

When the connection ID does not contain /, behaviour is byte-for-byte identical to before. No changes to tool schemas, no breaking changes to existing callers.

Example

// Workspace connection "my-pg" targets database "postgres" by default.

// Before: list_tables only sees "postgres"
{ "connectionId": "my-pg" }

// After: any DB on the same server, no extra workspace connection
{ "connectionId": "my-pg/analytics" }
{ "connectionId": "my-pg/billing" }
{ "connectionId": "my-pg/inventory" }

Tests

Added 8 new tests (53 total, all passing):

• parseConnectionId: no slash, single slash, empty halves, multiple slashes
• sanitizeConnectionId: preserves / for the override suffix
• getConnection: id lookup, name lookup, override applies database to all required fields, cache immutability, unknown base id returns null

npm run typecheck ✓ npm run lint ✓ npm test ✓ (53/53)

Test plan

• Typecheck passes
• Lint passes
• All existing tests still pass
• New unit tests cover the override happy-path, error paths, and immutability invariant
• Manually verified end-to-end against a real PostgreSQL RDS cluster: a single workspace connection (bound to postgres) successfully listed tables in 7 sibling databases via <id>/<database> syntax.