mmetl: timestamps are not precise enough

Description

When transforming a slack export file with several posts created close enough, the transformation of the post timestamp loses some precision, causing collisions in some cases.

If those posts have attachments, they are be added to the same post in the database and potentially cause the import to crash due too many attachments on the same post.

QA Test Steps

Talked offline

Mana

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Assignee

Miguel de la Cruz

QA Assignee

Sven Hüster

Reporter

Miguel de la Cruz

Epic Link

Fix versions

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Mattermost Team

Platform

Sprint

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Labels

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QA Testing Areas

Other (write in QA test steps)

GitHub Issue

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Components

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Severity

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