fix: Wrong interval functions for BigQuery

[lvauvillier]

Fix BigQuery error:

Dropping Cache: {
  "cacheKey": [
    "SELECT CASE\n    WHEN CURRENT_TIMESTAMP() < DATETIME_ADD(TIMESTAMP(?), INTERVAL 7 day) THEN FLOOR(UNIX_SECONDS(CURRENT_TIMESTAMP()) / 86400) END",
    [
      "2020-01-12T23:59:59Z"
    ]
  ]
} 
Error: No matching signature for function DATETIME_ADD for argument types: TIMESTAMP, INTERVAL INT64 DATE_TIME_PART. Supported signature: DATETIME_ADD(DATETIME, INTERVAL INT64 DATE_TIME_PART) at [2:32]

[paveltiunov]

@lvauvillier Thanks for contributing this one! DATETIME here may seem weird but it's correct implementation but probably wrong name right now. Bug is on this line: https://github.com/cube-js/cube.js/blob/c72ab079d53458b7377bc12f498667110af18689/packages/cubejs-schema-compiler/adapter/BaseQuery.js#L1533. So the solution is to introduce addTimestampInterval and subtractTimestampInterval methods which should use addInterval and subtractInterval in base implementation and should be overridden in BigqueryQuery.

[lvauvillier]

Thanks @paveltiunov. I have just pushed an update.

[paveltiunov]

@lvauvillier Looks great! Thanks again!