No way to specify a value for external-dns --txt-prefixor --txt-suffix

[mscottford]

The external-dns service is configured to use TXT DNS records to keep track of the A and CNAME records it has created in the hosted zone. The default name of the TXT record is the same as the name of the A/CNAME record.

This causes problems in scenarios where TXT records already exist, because external-dns generates an error in that case (see sample below). One reason that a TXT record might already exist is to comply with DNS validation checks for 3rd party services, such as Google Workspace or GMail.

To assist with this problem, external-dns supports a txt-prefix and txt-suffix parameter.

I propose that these values become available in the Massdriver configure UI when managing a bundle. It probably makes sense to place them behind an "advanced" configuration setting. I further propose that a prefix of edns. becomes the default. This would avoid the surprise that I ran into this week for newcomers, while also allowing folks the option of reverting to the previous behavior. It's worth noting that the external-dns docs discourage changing the txt-prefix or txt-suffix values after external-dns is installed in a cluster, because it may affect its ability to make DNS changes. For that reason, it might make sense to make these values read only after the bundle has been deployed.

(Note: The actual domain and hostedzone id have been redacted.)

│ time="2023-10-28T06:51:11Z" level=info msg="Applying provider record filter for domains: [example.io. .example.io.]"                                         │
│ time="2023-10-28T06:51:11Z" level=info msg="Desired change: DELETE www.example.io A [Id: /hostedzone/Z9999999999999]"                                 │
│ time="2023-10-28T06:51:11Z" level=info msg="Desired change: DELETE www.example.io TXT [Id: /hostedzone/Z9999999999999]"                               │
│ time="2023-10-28T06:51:11Z" level=info msg="Desired change: CREATE example.io A [Id: /hostedzone/Z9999999999999]"                                     │
│ time="2023-10-28T06:51:11Z" level=info msg="Desired change: CREATE example.io TXT [Id: /hostedzone/Z9999999999999]"                                   │
│ time="2023-10-28T06:51:11Z" level=error msg="Failure in zone example.io. [Id: /hostedzone/Z9999999999999]"                                            │
│ time="2023-10-28T06:51:11Z" level=error msg="InvalidChangeBatch: [Tried to create resource record set [name='example.io.', type='TXT'] but it already exists │
│ time="2023-10-28T06:51:11Z" level=error msg="failed to submit all changes for the following zones: [/hostedzone/Z9999999999999]"                      │
│