adding a feature to customize the egress rule

[haidargit]

what

• Added 4 new variables egress_source_port, egress_dest_port, egress_protocol, and allowed_egress_cidr_blocks for the "aws_security_group_rule" "egress" resource.
• By default, the egress rule 0.0.0.0/0 will be created. If user is expected to restrict outbound traffic, they can specify the required values.

why

• We propose this PR because there are scenarios where users may want to restrict outbound traffic from their DocDB instances.
• if the DocDB cluster is only used internally and do not need to communicate with wide systems or network, users may want to customize the egress rule for 0.0.0.0/0. By providing the option to customize the egress rule, we are giving users a control over their security posture (compliance). For example, our docdb may only connected with internal applications inside the aws eks cluster, or users may integrate their cloud resources with a third party, such as Prisma Cloud or maybe use tfsec as their security scanner, which prompts users to kindly avoid 0.0.0.0/0 for security best practices.

references

• This PR will help to cover the minimum egress exposure of the security group, including: allow optional / no egress security rule #34

Thank you

[milldr]

/terratest

[milldr]

LGTM! Thanks for the contribution

[haidargit]

@milldr thanks Pal!