Add streetteam postmark template

[michael-jeremiah-walker]

Description

Adds a new Domain Connect template for StreetTeam (streetteam.fm) to configure custom email sending domains via Postmark.

The template configures:

• DKIM authentication (TXT record) for email signing
• Return-Path (CNAME record) for bounce handling

Type of change

• New template
• Bug fix (non-breaking change which fixes an issue in the template)
• New feature (non-breaking change which adds functionality to the template)
• Breaking change (fix or feature that would cause existing template behavior to be not backward compatible)

How Has This Been Tested?

• Schema validated using JSON Schema template.schema
• Template functionality checked using Online Editor
• Template is checked using template linter
• Template file name follows the pattern <providerId>.<serviceId>.json
• resource URL provided with logoUrl is actually served by a webserver

Example variable values

dkimSelector: 20221024112549pm
dkimValue: k=rsa;p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQExample
returnPathHost: pm-bounces
returnPathValue: pm.mtasv.net

"testData": {
  "postmark-example": {
    "variables": {
      "domain": "example.com",
      "host": "",
      "dkimSelector": "20221024112549pm",
      "dkimValue": "k=rsa;p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQExample",
      "returnPathHost": "pm-bounces",
      "returnPathValue": "pm.mtasv.net"
    },
    "results": [
      {
        "type": "TXT",
        "name": "20221024112549pm._domainkey",
        "ttl": 3600,
        "data": "k=rsa;p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQExample"
      },
      {
        "type": "CNAME",
        "name": "pm-bounces",
        "ttl": 3600,
        "data": "pm.mtasv.net"
      }
    ]
  }
}

[github-actions]

Linter OK:

Linter result for streetteam.fm.postmark-email.json