Create Post-ToSlack cmdlet and token file

Signed-off-by: Chris Wahl <github@wahlnetwork.com>

Slack/Post-ToSlack.ps1

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+#requires -Version 3
+
+function Post-ToSlack 
+{
+    <#  
+            .SYNOPSIS
+            Sends a chat message to a Slack organization
+            .DESCRIPTION
+            The Post-ToSlack cmdlet is used to send a chat message to a Slack channel, group, or person.
+            Slack requires a token to authenticate to an org. Either place a file named token.txt in the same directory as this cmdlet,
+            or provide the token using the -token parameter. For more details on Slack tokens, use Get-Help with the -Full arg.
+            .NOTES
+            Written by Chris Wahl for community usage
+            Twitter: @ChrisWahl
+            GitHub: chriswahl
+            .EXAMPLE
+            Post-ToSlack -channel '#general' -message 'Hello everyone!' -botname 'The Borg'
+            This will send a message to the #General channel, and the bot's name will be The Borg.
+            .EXAMPLE
+            Post-ToSlack -channel '#general' -message 'Hello everyone!' -token '1234567890'
+            This will send a message to the #General channel using a specific token 1234567890, and the bot's name will be default (PowerShell Bot).
+            .LINK
+            Validate or update your Slack tokens:
+            https://api.slack.com/tokens
+            Create a Slack token:
+            https://api.slack.com/web
+            More information on Bot Users:
+            https://api.slack.com/bot-users
+    #>
+
+    Param(
+        [Parameter(Mandatory = $true,Position = 0,HelpMessage = 'Slack channel')]
+        [ValidateNotNullorEmpty()]
+        [String]$Channel,
+        [Parameter(Mandatory = $true,Position = 1,HelpMessage = 'Chat message')]
+        [ValidateNotNullorEmpty()]
+        [String]$Message,
+        [Parameter(Mandatory = $false,Position = 2,HelpMessage = 'Slack API token')]
+        [ValidateNotNullorEmpty()]
+        [String]$token,
+        [Parameter(Mandatory = $false,Position = 3,HelpMessage = 'Optional name for the bot')]
+        [String]$BotName = 'PowerShell Bot'
+    )
+
+    Process {
+
+        # Static parameters
+        if (!$token) 
+        {
+            $token = Get-Content -Path "$PSScriptRoot\token.txt"
+        }
+        $uri = 'https://slack.com/api/chat.postMessage'
+
+        # Build the body as per https://api.slack.com/methods/chat.postMessage
+        $body = @{
+            token    = $token
+            channel  = $Channel
+            text     = $Message
+            username = $BotName
+            parse    = 'full'
+        }
+
+        # Call the API
+        try 
+        {
+            Invoke-RestMethod -Uri $uri -Body $body
+        }
+        catch 
+        {
+            throw 'Unable to call the API'
+        }
+
+    } # End of process
+} # End of function

Slack/token.txt

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+Put your token in here and remove all other text!
+
+Validate or update your Slack tokens:
+https://api.slack.com/tokens
+Create a Slack token:
+https://api.slack.com/web