prepare the transition to #Plan.context

This change helps the transition between `dagger input` and `#Plan.context`.

In summary, the codebase now relies on a *context* for execution with mapping to *IDs*.
In the future, *context* will come from a `#Plan.context`.
In the meantime, a bridge converts `dagger input` to a plan context. This allows both *old* and *new* style configurations to co-exist with the same underlying engine.

- Implement `plancontext`. Context holds the execution context for a plan. Currently this includes the platform, local directories, secrets and services (e.g. unix/npipe).
- Contextual data can be registered at any point. In the future, this will be done by `#Plan.context`
- Migrated the `dagger input` codebase to register inputs in a `plancontext`
- Migrated low-level types/operations to the *Context ID* pattern.
  - `dagger.#Stream` now only includes an `id` (instead of `unix` path)
  - `dagger.#Secret` still includes only an ID, but now it's based off `plancontext`
  - `op.#Local` now only includes an `id` (instead of `path`, `include`, `exclude`.

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

solver/solver.go

@@ -18,6 +18,7 @@ import (
 	"github.com/opencontainers/go-digest"
 	specs "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/rs/zerolog/log"
+	"go.dagger.io/dagger/plancontext"
 )
 
 type Solver struct {
@@ -27,12 +28,12 @@ type Solver struct {
 }
 
 type Opts struct {
-	Control      *bk.Client
-	Gateway      bkgw.Client
-	Events       chan *bk.SolveStatus
-	Auth         *RegistryAuthProvider
-	SecretsStore SecretsStore
-	NoCache      bool
+	Control *bk.Client
+	Gateway bkgw.Client
+	Events  chan *bk.SolveStatus
+	Context *plancontext.Context
+	Auth    *RegistryAuthProvider
+	NoCache bool
 }
 
 func New(opts Opts) Solver {
@@ -194,8 +195,8 @@ func (s Solver) Export(ctx context.Context, st llb.State, img *dockerfile2llb.Im
 		Exports: []bk.ExportEntry{output},
 		Session: []session.Attachable{
 			s.opts.Auth,
-			s.opts.SecretsStore.Secrets,
-			NewDockerSocketProvider(),
+			NewSecretsStoreProvider(s.opts.Context),
+			NewDockerSocketProvider(s.opts.Context),
 		},
 	}