Port the "user activate" subcommand from Mattermost CLI to mmctl

Description

This ticket includes the creation of a "user activate" subcommand in mmctl based on the Mattermost CLI command that can be found in cmd/mattermost/commands/user.go.

To achieve this, the command can use the Update User Active status endpoint, and it should mimic the structure, arguments and behavior of the Mattermost CLI command.

QA Test Steps

None

Status

Mana

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Assignee

Mattermost Community

QA Assignee

None

Reporter

Miguel de la Cruz

Epic Link

Fix versions

Mattermost Team

Platform

Sprint

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Labels

None

QA Testing Areas

CLI

Components

None
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