build(deps): bump date-fns from 2.6.0 to 2.7.0 in /backend

Sourced from date-fns's releases.

v2.7.0

Thanks to @​mzgajner, @​NaridaL, @​Zyten, @​leshakoss, @​fintara and @​kpr-hellofresh for contributing to the release.

Fixed

• Fixed a mistake in the Slovenian locale.
• Fixed incorrect behavior of parseISO in Firefox caused by differences in getTimezoneOffset.

Changed

• Make object argument types more elaborate in Flow type definitions.
• Get rid of deprecated Function in Flow type definitions.
• Allow parseJSON to accept strings without trailing 'Z' symbol and with up to 6 digits in the milliseconds' field.

Added

• Added Bulgarian (bg) locale.

Sourced from date-fns's changelog.

[2.7.0] - 2019-11-07

Thanks to @​mzgajner, @​NaridaL, @​Zyten, @​leshakoss, @​fintara, @​kpr-hellofresh for contributing to the release.

Fixed

• Fixed a mistake in the Slovenian locale.
• Fixed incorrect behavior of parseISO in Firefox caused by differences in getTimezoneOffset.

Changed

• Make object arguments types more elaborate in Flow type definitions.
• Get rid of deprecated Function in Flow type definitions.
• Allow parseJSON to accept strings without trailing 'Z' symbol and with up to 6 digits in the milliseconds' field.

Added

• Added Bulgarian (bg) locale.

• aa1daea Update the v2.7.0 changelog entry
• bd40408 Add change log entry for v2.7.0
• 7188ea5 Make parseJSON to accept more standard formats (#1496) (#1499)
• d747d12 Round timezones offset in getTimezoneOffsetInMilliseconds (#1495) (closes #1310)
• a1e6aff Add the Bulgarian (bg) locale (#1522) (closes #1442)
• 23b2703 Get rid of Function in Flow type definitions (#1520)
• 90a2242 Make object arguments types more elaborate in Flow type definitions (#1519)
• 750a8e9 Improve roundToNearestMinutes doc (#1516)
• 986f548 Improve areIntervalsOverlapping doc (#1505)
• 2b59089 Fix a mistake in the Slovenian locale (#1529)
• Additional commits viewable in compare view

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