ELBv2: Fix CF bug when passing certificates to ELB listener creation

[Ivan-Lukianov]

Context:

Recently our tests started failing with a next error:

pattern = '^arn:(aws|aws-cn|aws-iso|aws-iso-b|aws-us-gov):iam:'
string = [{'CertificateArn': 'arn:aws:acm:us-east-1:123456789012:certificate/<cert_id>', 'certificate_arn': 'arn:aws:acm:us-east-1:123456789012:certificate/<cert_id>'}]
flags = 0

    def search(pattern, string, flags=0):
        """Scan through string looking for a match to the pattern, returning
        a Match object, or None if no match was found."""
>       return _compile(pattern, flags).search(string)
E       TypeError: expected string or bytes-like object, got 'list'

I tracked down an issue to this change - #8054

In my understanding in case of listener creation from cloudformation certificate variable is not a string, but an array and this newly added code is failing.

This PR adds a change so certificate passed as a string to create_listener method in cloudformation case similar to what is in the elb client code.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.46%. Comparing base (b574a9a) to head (c0d1837).
Report is 6 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #8106   +/-   ##
=======================================
  Coverage   94.45%   94.46%           
=======================================
  Files        1141     1141           
  Lines       98198    98201    +3     
=======================================
+ Hits        92757    92761    +4     
+ Misses       5441     5440    -1     

Flag	Coverage Δ
servertests	28.95% <0.00%> (-0.01%)	⬇️
unittests	94.43% <100.00%> (+<0.01%)	⬆️

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[bblommers]

Hi @Ivan-Lukianov, thank you for the fix and for adding the test case!

It is an interesting decision from AWS to require a list of certificates, and at the same time state that You must provide exactly one certificate...
But with that in mind, the if/else statement that always picks the first certificate makes sense.

[github-actions]

This is now part of moto >= 5.0.15.dev2