Add ability to scan snaps (as a source) (#3929)

syft/format/syftjson/model/source_test.go

@@ -145,6 +145,51 @@ func TestSource_UnmarshalJSON(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "snap",
+			input: []byte(`{
+  "id": "foobar",
+  "name": "etcd",
+  "version": "3.4.36",
+  "type": "snap",
+  "metadata": {
+    "summary": "Distributed reliable key-value store",
+    "base": "core18",
+    "grade": "stable",
+    "confinement": "strict",
+    "architectures": [
+      "amd64"
+    ],
+    "digests": [
+      {
+        "algorithm": "sha256",
+        "value": "6700d789d2c38b0f7513058ddcea8f9a275e2206b4621a772eb065e12069956e"
+      }
+    ]
+  }
+}`),
+			expected: &Source{
+				ID:      "foobar",
+				Name:    "etcd",
+				Version: "3.4.36",
+				Type:    "snap",
+				Metadata: source.SnapMetadata{
+					Summary:     "Distributed reliable key-value store",
+					Base:        "core18",
+					Grade:       "stable",
+					Confinement: "strict",
+					Architectures: []string{
+						"amd64",
+					},
+					Digests: []file.Digest{
+						{
+							Algorithm: "sha256",
+							Value:     "6700d789d2c38b0f7513058ddcea8f9a275e2206b4621a772eb065e12069956e",
+						},
+					},
+				},
+			},
+		},
 		{
 			name: "unknown source type",
 			input: []byte(`{