Move source-related queries from `Invoke()` function into Source.
The following sources are updated in this PR:
* couchbase
* dgraph
* elasticsearch
* firebird
This is an effort to generalizing tools to work with any Source that
implements a specific interface. This will provide a better segregation
of the roles for Tools vs Source.
Tool's role will be limited to the following:
* Resolve any pre-implementation steps or parameters (e.g. template
parameters)
* Retrieving Source
* Calling the source's implementation
To keep a persistent backend storage for configuration, we will have to
keep a single source of truth. This involves supporting bi-directional
conversion between Config and Source.
This PR make the following changes:
* Embed Config in Source
* Add `ToConfig()` to extract Config from Source.
This commit refactors the source configuration and loading mechanism to
use a dynamic registration pattern. Each source package now registers
itself with a central registry via its init() function.
The server configuration code uses this registry to decode and
initialize sources, decoupling it from specific source implementations
and simplifying the addition of new sources.
Key changes:
- Introduced `sources.Register()` and `newConfig()` constructor in each
source package.
- Moved source package imports to `cmd/root.go` as blank imports to
trigger `init()` functions for self-registration.
- Removed direct imports of specific source packages from
`internal/server/config.go`.
- Renamed `SourceKind` constants to `Kind` within each source package.
- Updated tests to use the new `Kind` constants and reflect registration
changes.
---------
Co-authored-by: Yuan Teoh <yuanteoh@google.com>
