Add relaydns.dev.relay-connect template

[endibuka]

Description

New template for RelayDNS. It points a customer-supplied subdomain at a RelayDNS
relay host and adds the verification TXT record for that setup, so an end user can
connect a domain without editing DNS by hand.

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?

Please mark the following checks done

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

Checklist of common problems

• syncPubKeyDomain is set — this is mandatory
• warnPhishing is not set alongside syncPubKeyDomain
• syncRedirectDomain is set whenever the template uses redirect_uri
• no TXT record contains SPF content
• txtConflictMatchingMode is set on every TXT record that must be unique
• no variable is used as a bare full record value — justified below
• no bare variable is used as the full host label
• no variable is used in the host field to create a subdomain
• %host% does not appear explicitly in any host attribute
• essential is set to OnApply on records the end user may need to modify — see note below

Justification — bare variable as a full record value.
The CNAME uses "pointsTo": "%target%". A CNAME's value is by definition a complete
hostname, so unlike a TXT record there is no fixed prefix available to scope it with;
service-foo=%foo% has no CNAME equivalent. The variable is constrained on our side
instead: the service only ever emits relay hostnames we operate, and every apply URL
is RSA-SHA256 signed against the key published at _dcpubkeyv1.relaydns.dev, so a
third party cannot substitute a target of their own.

Note — essential.
Deliberately not set. Neither record is user-modifiable: removing or editing either
breaks the setup rather than degrading it, so OnApply would misrepresent them.

Note — hostRequired.
Set to true. The template places a CNAME at host: "@", and a CNAME on a zone apex
is invalid DNS, so a host must be supplied at apply time. Verified in the editor: an
apply with no host is refused with "Template requires a host name". Per the exception
in the PR template, no apex test link is included.

Note — linter DCTL1031 (shared groupId).
Intentional. Both records carry groupId: "relay" because they are meaningless
apart — a CNAME without its verification TXT produces a domain that is configured
but can never be verified. They must be applied together, not offered as independent
options.

Online Editor test results

Editor test link(s):
https://domainconnect.paulonet.eu/dc/free/templateedit?token=H4sIAMh7iWoC%2F%2B1UXW%2FbOgz9K4KAPsX27HRNGwMD9pE97N7brusybENRBIrF2FodyVei03hF%2F%2FsoOx%2FOWux5A%2FZmieTxOeSh7jnCsioFAk%2FveWXNSkmw7yRPuYVSNFK7SMKKB7vYhVhSLr%2Fy0cnFR4o4sCuVwb4ozIzWkOE%2Btil6090zwaRZCqUZGtYDWoF1ymieJgEvjMMr%2BL9WFggXbQ0BL01uPtmSgArEyqXPnvU57g6hzwuNDkuVFxi5VU7YElxmVYUtPr80SqMjHlnt0CzBMlfPN5wE7jgxoSUTUjqGBTCipxYqEx6DWciMlWxhLMWoxAHWVeRFCKvEvITJwQ9R2BwwbXF26C1h5pVq6g%2FFlOvxcIWpS8kqT5VIBQyiPOpqor7uiLp4C7rDrsCGLZVDtm1GwApYB0w5V4NkdwXotsQzceB85ynGMgvkBumluEZnl%2FX8X2gmLaXHpvAZr0uT3fJ0IUoH3c0VSBpbhrsqUakDysFPMF0zHU%2Bv7zk2VWuVi1fnbymUW1NXe2vxzhl0fOk92Y5xauh41HX4iG4RySLHozh%2BCHZw0y%2FTX4HNtoS8UwSKntKwbWTz4qjt4QE%2Bfa6RPL0oVYbnArNC6fzcSP%2FDSwsLteZPpmxij%2F%2FBH24eAv7daJjtW3JDlLaNvC0bG5VK3%2B6p52YrbKa2%2BZWwYun8Rm8rr3ulN9vaa19Mp651%2FrxZ3INhtRleu09wKtcgERyeno25Z0sXxsLMBwTWFrbLuqxLVDNxJ%2FZXMpuJqiobEucoSniP5627l6JVtZnEk6QOxjCTmRer%2FGSz58NFvEhG4WmSnIbPR%2BNReJYMk3CUxPPk%2BPhkvIjnvefsqafuVw9av%2Bu0NKBRCf8ivSrvROP4wyPPbQTtHBb1pf1sgMP2%2FrYabwJy2d%2FZ%2FZmzo3V2YgVyJnziMB6OwvgsHA6nSUx005NRdHw6PInHgzhO49gLIUmd5nva9%2F6m86%2BT9ZtPg8t1%2Ffod6sH424dmfP4fzicCzUBPC1VN%2Fnl%2FN%2FiM7wc5PW4%2FAFUM6jRtCAAA

[github-actions]

✅ JSON Filename Check Passed

[github-actions]

✅ JSON Schema Validation Passed

[github-actions]

Linter OK

relaydns.dev.relay-connect.json

Level	Code	Note
info	DCTL1021	missing from iana definitions
info	DCTL1031	all record groupId values are the same

[github-actions]

PR Description Check Passed

All required sections are filled in correctly.

Details

  OK  Type of change: 1/4 checkboxes ticked
  OK  How Has This Been Tested?: all 3 checkboxes ticked
  OK  Checklist of common problems: 10/10 checkboxes ticked
  OK  Online Editor test results: 1 link(s) found
  OK  Template coverage: all 1 template(s) covered
Labels to remove: Checklist of common problems not complete, Forged editor links, PR description incomplete, Test links missing

PR description check PASSED