feat: warn if parsing newer SBOM (#1810)

If syft is asked to parse an SBOM that was written by a newer version of
syft, emit a warning, since the current version of syft doesn't know about 
fields that may be added in the future.

Signed-off-by: Will Murphy <will.murphy@anchore.com>

syft/formats/syftjson/decoder_test.go

@@ -2,6 +2,8 @@ package syftjson
 
 import (
 	"bytes"
+	"errors"
+	"fmt"
 	"strings"
 	"testing"
 
@@ -49,3 +51,38 @@ func TestEncodeDecodeCycle(t *testing.T) {
 		}
 	}
 }
+
+func TestOutOfDateParser(t *testing.T) {
+	tests := []struct {
+		name            string
+		documentVersion string
+		parserVersion   string
+		want            error
+	}{{
+		name:            "no warning when doc version is older",
+		documentVersion: "1.0.9",
+		parserVersion:   "3.1.0",
+	}, {
+		name:            "warning when parser is older",
+		documentVersion: "4.3.2",
+		parserVersion:   "3.1.0",
+		want:            fmt.Errorf("document has schema version %s, but parser has older schema version (%s)", "4.3.2", "3.1.0"),
+	}, {
+		name:            "warning when document version is unparseable",
+		documentVersion: "some-nonsense",
+		parserVersion:   "3.1.0",
+		want:            fmt.Errorf("error comparing document schema version with parser schema version: %w", errors.New("Invalid Semantic Version")),
+	}, {
+		name:            "warning when parser version is unparseable",
+		documentVersion: "7.1.0",
+		parserVersion:   "some-nonsense",
+		want:            fmt.Errorf("error comparing document schema version with parser schema version: %w", errors.New("Invalid Semantic Version")),
+	}}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := checkSupportedSchema(tt.documentVersion, tt.parserVersion)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}