Introduce support for Slack Enterprise Grid

[coltoneshaw]

Summary

This PR introduces support for Slack Enterprise grid within mmetl.

How to use this PR

Simply provide it a slack grid export and an accompanying teams.json file.

./mmetl grid-transform -f slackexport.zip -t teams.json

Teams file example. T0001 is the team ID that is found within a post at post.Team. teamx is the name of the team, which corresponds to the folder name inside teams/.

{
  "T0001" : "team1",
  "T0002" : "team2",
}

What is Enterprise Grid?

It's a collection of slack workspaces under a single organization within Slack. They are able to share channels across slack workspaces and collaborate this way.

The files structure is like:

Enterprise Grid Export/
├── channel1/
│   ├── 2023-01-01.json
│   └── 2023-01-02.json
├── channel2/
│   ├── 2023-05-01.json
│   └── 2023-05-02.json
├── teams/
│   ├── team1/
│   │   ├── channel3/
│   │   │   ├── 2023-05-01.json
│   │   │   └── 2023-05-02.json
│   │   ├── channels.json
│   │   ├── mpims.json
│   │   ├── dms.json
│   │   ├── users.json
│   │   └── groups.json
│   └── team2/
│       ├── channel4/
│       │   ├── 2023-05-01.json
│       │   └── 2023-05-02.json
│       ├── channels.json
│       ├── mpims.json
│       ├── dms.json
│       ├── users.json
│       └── groups.json
├── channels.json
├── org_users.json
├── mpims.json
├── dms.json
└── groups.json

What does this do?

This PR simply processes the enterprise grid export file by parsing the root level channels for the appropriate team, and placing them there. Then when done, zipping up every team folder as a separate slack export.

How do we know where the channels belong?

For the most part, every channel has a post that has a Team attribute on it, like below. These team attributes are used to identify the originating team from the channel and move it there. The appropriate .json file is then updated with the new information. If for whatever reason a matching team is not found, that item is skipped on the import entirely.

    {
        "client_msg_id": "",
        "type": "",
        "text": "",
        "user": "U1",
        "ts": "1695219722.430309",
        "blocks": [  ],
        "team": "team1",
        "user_team": "team1",
        "source_team": "team1",
        "user_profile": { }
    },

Potential Gaps

One potential gap is that this does not go down the list of channel members and repopulate the users.json with the members from the org_users.json file. The reason is they will most likely be imported multiple teams into their space anyways, so those users would be filled out and added properly. However, it wouldn't be a difficult thing to add here.

[mickmister]

LGTM, just some comments for discussion. Nice work!