feat(apply): load template file

[wafuwafu13]

Issue #, if available:

#155 (comment)

[apply] Load template file

• Load cfn.yaml or cfn.yml or cfn.json in the same hierarchy where the dy command is executed

  • It is like main.tf in Terraform

• If not exist, exit(1)

command:

~/path/to/foo
$ ls
cfn.yaml

~/path/to/foo
(for now, just checking existence of file)
$ dy admin apply --dev

Description of changes:

• implement apply function and check_template function
• mock Path::new(path).exists() for testing

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[wafuwafu13]

test_apply_without_acceptable_file is covered in test/apply.rs#test_apply_with_dev