Add a new docker image used to generate code

[nghialv]

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

A Kapetanios build has just been triggered to run docker operations for the following 1 directory.
Their results will be reported back after the build is completed.

1. dockers/codegen

[pipecd-bot]

The Kapetanios build to run docker operations for the following 1 directory has been completed.

1. dockers/codegen - success

An image named codegen:0.1.0-7a34523 was procuded for reviewing and testing.
By merging this PR, an image named codegen:0.1.0 will be pushed to the container registry.

There is no test to run inside this directory.

[khanhtc1202]

nits, without container name, I think we should add --rm to remove the container after it exits

[nghialv]

Nice catch! 💯

[pipecd-bot]

A Kapetanios build has just been triggered to run docker operations for the following 1 directory.
Their results will be reported back after the build is completed.

1. dockers/codegen

[pipecd-bot]

The Kapetanios build to run docker operations for the following 1 directory has been completed.

1. dockers/codegen - success

An image named codegen:0.1.0-8dc84ff was procuded for reviewing and testing.
By merging this PR, an image named codegen:0.1.0 will be pushed to the container registry.

There is no test to run inside this directory.

[pipecd-bot]

Code coverage for golang is 32.39%. This pull request does not change code coverage.

[khanhtc1202]

Nice improvement 🙌
/approve

[pipecd-bot]

This pull request is APPROVED by khanhtc1202.

Approvers can cancel the approval by writing /approve cancel in a comment. Any additional commits also will change this pull request to be not-approved.