Add the DNS mapping migration

[fritzmg]

Alternative approach to #4077 and #4583. This allows you to define mappings via a DNS_MAPPING environment variable which will update the dns entries for all given domains to the updated domain in the database during migrations.

# .env.local in your local environment
DNS_MAPPING='{
    "www.example.com": "example.local",
    "www.foobar.org": "foobar.local",
    "www.lorem.at": "lorem.local"
}'

# .env.local in your staging environment
DNS_MAPPING='{
    "www.example.com": "staging.example.com",
    "www.foobar.org": "staging.foobar.org",
    "www.lorem.at": "staging.lorem.at"
}'

This allows you to - for example - copy the live database to your staging or local environment and then automatically change the domains according to the mapping in the respective environment during contao:migrate.

As a bonus you can also migrate the useSSL setting to different settings in the respective environment, which might be useful if you haven't set up an SSL certificate in your local development environment.

DNS_MAPPING='{
    "www.example.com": "http://example.local",
    "www.foobar.org": "http://foobar.local",
    "www.lorem.at": "http://lorem.local"
}'

This also works if you do not use a dns name in some of your website roots (although that is not a recommended setup).

DNS_MAPPING='{
    "": "http://",
    "www.foobar.org": "http://foobar.local",
    "www.lorem.at": "http://lorem.local"
}'

DNS_MAPPING='{
    "": "example.local",
    "www.foobar.org": "foobar.local",
    "www.lorem.at": "lorem.local"
}'

Instead of the environment variable, you can also directly set the parameter in your parameters.yaml (or wherever):

parameters:
    contao.dns_mapping:
        www.example.com: http://example.local
        www.foobar.org: http://foobar.local
        www.lorem.at: http://lorem.local

[fritzmg]

As discussed in the last call, the definition of the environment variable has now been moved to the Manager Bundle. However, it is not possible to also provide this as a bundle configuration, as you cannot reference an environment variable for array config nodes yet (see symfony/symfony#40906). Thus this is again solely based on a contao.dns_mapping parameter.

The core bundle checks whether such a parameter has been defined in the container and if not sets an empty default. The manager bundle also checks whether such a parameter has been defined in the container (e.g. in the App) and if not sets it to the DNS_MAPPING environment variable.

[fritzmg]

In a non-managed edition you will have to add this to your config (if you want to use an environment variable for the parameter):

parameters:
    env(DNS_MAPPING): []
    contao.dns_mapping: '%env(json:DNS_MAPPING)%'

[Toflar]

I would personally add a TODO and link to the Symfony issue so that we can get rid of the workaround if this was fixed eventually but other than that 👍

[fritzmg]

As discussed in the Contao call today, the contao.dns_mapping parameter definition has now been moved to the migrations.yaml with its default empty value. And the contao.dns_mapping parameter override via the DNS_MAPPING environment variable has been moved to the skeleton config in the Manager Bundle.

[leofeyer]

Thank you @fritzmg.