ICU-745/Refactor internal/session to new domain errors (#877)

* Refactor internal/sessions to use domain errors

internal/errors/code_test.go

@@ -77,6 +77,21 @@ func TestCode_Both_String_Info(t *testing.T) {
 			c:    InvalidTimeStamp,
 			want: InvalidTimeStamp,
 		},
+		{
+			name: "SessionNotFound",
+			c:    SessionNotFound,
+			want: SessionNotFound,
+		},
+		{
+			name: "InvalidSessionState",
+			c:    InvalidSessionState,
+			want: InvalidSessionState,
+		},
+		{
+			name: "TokenMismatch",
+			c:    TokenMismatch,
+			want: TokenMismatch,
+		},
 		{
 			name: "PasswordTooShort",
 			c:    PasswordTooShort,
@@ -117,6 +132,16 @@ func TestCode_Both_String_Info(t *testing.T) {
 			c:    Decode,
 			want: Decode,
 		},
+		{
+			name: "GenKey",
+			c:    GenKey,
+			want: GenKey,
+		},
+		{
+			name: "GenCert",
+			c:    GenCert,
+			want: GenCert,
+		},
 		{
 			name: "CheckConstraint",
 			c:    CheckConstraint,