docker-php-ext-configure ldap should fail when libldap-common is not available

[thinkl33t]

Since the change reported in #1194, and tracked down in #1194 (comment) , we have encountered multiple pieces of containerized PHP software that have been failing to connect to LDAP, and they have all led back to this common issue.

Since it is non-obvious to developers that installing the ldap module will require this dependency, i suggest either:

1. install it by default in the php debian-based containers
2. install it on demand when docker-php-ext-configure ldap is run
3. cause installation to fail if it is not installed when docker-php-ext-configure ldap is run

I think (1) would be the easiest, but obviously adds a dependency that would be unwanted in a lot of installations.

[thinkl33t]

Note: this effects LDAP with TLS - I believe insecure LDAP still works OK, but shouldn't be used for obvious reasons.

[yosifkit]

1. install it by default in the php debian-based containers

While the package is very small (https://packages.debian.org/buster/libldap-common), we do not install extra packages for extensions that aren't enabled by default.

2. install it on demand when docker-php-ext-configure ldap is run

We do not want to maintain the extension to required packages mapping; that is the goal of https://github.com/mlocati/docker-php-extension-installer. (it looks like they have not updated to ensure libldap-common, so maybe an issue or PR there would help others)

3. cause installation to fail if it is not installed when docker-php-ext-configure ldap is run

Detecting if it is installed would be maintaining the same map as auto-installing it; see previous answer.

[thinkl33t]

I have opened an issue upstream with docker-php-extension-installer

[thinkl33t]

I have added libldap-common to ldap on docker-php-extension-installer, but I can't find any way in which the php container specifications here actually consume that script? Am i missing something or is it completely unrelated?

[phy25]

https://github.com/mlocati/docker-php-extension-installer#usage

"php" does not consume "docker-php-extension-installer".

[tianon]

We do not want to maintain the extension to required packages mapping; that is the goal of https://github.com/mlocati/docker-php-extension-installer.

🙈 ❤️