Split the sbom.Format interface by encode and decode use cases (#2186)

* split up sbom.Format into encode and decode ops

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* update cmd pkg to inject format configs

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* bump cyclonedx schema to 1.5

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* redact image metadata from github encoder tests

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* add more testing around format decoder identify

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* add test case for format version options

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* fix cli tests

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* fix CLI test

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* [wip] - review comments

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* keep encoder creation out of post load function

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* keep decider and identify functions

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* add a few more doc comments

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* remove format encoder default function helpers

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* address PR feedback

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* move back to streaming based decode functions

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* with common convention for encoder constructors

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* fix tests and allow for encoders to be created from cli options

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* fix cli tests

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* fix linting

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* buffer reads from stdin to support seeking

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

---------

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

syft/format/github/encoder.go

@@ -0,0 +1,42 @@
+package github
+
+import (
+	"encoding/json"
+	"io"
+
+	"github.com/anchore/syft/syft/format/github/internal/model"
+	"github.com/anchore/syft/syft/sbom"
+)
+
+const ID sbom.FormatID = "github-json"
+
+type encoder struct {
+}
+
+func NewFormatEncoder() sbom.FormatEncoder {
+	return encoder{}
+}
+
+func (e encoder) ID() sbom.FormatID {
+	return ID
+}
+
+func (e encoder) Aliases() []string {
+	return []string{
+		"github",
+	}
+}
+
+func (e encoder) Version() string {
+	return sbom.AnyVersion
+}
+
+func (e encoder) Encode(writer io.Writer, s sbom.SBOM) error {
+	bom := model.ToGithubModel(&s)
+
+	enc := json.NewEncoder(writer)
+	enc.SetEscapeHTML(false)
+	enc.SetIndent("", "  ")
+
+	return enc.Encode(bom)
+}