Interleaved table relationships are not included in a generated snapshot

[olavloite]

Descripton:

Interleaved table relations are not included in generated change logs when taking a snapshot of an existing database.

Steps to reproduce:

Use for example DDL as below to create new table on Spanner:

CREATE TABLE TEST (
  TEST_LOC STRING(8) NOT NULL,
) PRIMARY KEY(TEST_LOC);

CREATE TABLE TEST_CONTNT (
  TEST_LOC STRING(8) NOT NULL,
) PRIMARY KEY(TEST_LOC),
  INTERLEAVE IN PARENT TEST ON DELETE CASCADE;

Then run:
liquibase --url="jdbc:cloudspanner:/projects/<project>/instances/<instance>/databases/<database>" --changeLogFile=changeLog.yml generateChangeLog

The generated change log will contain both tables, but the INTERLEAVE IN PARENT clause of the child table will not be generated.

Originally reported in #78. The problem that these relations were generated as a nameless foreign key has been fixed.