Correct docker repository for the ingestion server, update docs

[AetherUnbound]

Description

This PR corrects the docker repository name used in production for the ingestion server. This format changed as a part of #437. It also adds a way to easily override the desired tag using an environment variable (in this case, in the local .env file on production). This way we can specify which version we want to pull/run without having to update the file on every version bump.

Lastly, I added some documentation to the DNS segment based on discussion in #346.

Testing Instructions

1. cd ingestion_server
2. docker-compose pull (optionally setting the IMAGE_TAG variable to a specific version tag, e.g. v2.1.1)
3. docker-compose up -d

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the default branch of the repository (main) or a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.

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[dhruvkb]

TIL about environment variable interpolation inside docker-compose.yml! Very cool 👍

[AetherUnbound]

TIL about environment variable interpolation inside docker-compose.yml! Very cool +1

We were trying to come up with a solution on a different project for pinning the version in the prod compose file without having to change the text and this fit the bill perfectly!

[obulat]

When running docker-compose pull, I am getting this error:
open ...openverse-api/ingestion_server/.env: no such file or directory . Do I need to create a .env file before running?

I just copied env.docker as .env and it seems to work. Edited: It does work, and the container runs fine:

docker-compose up -d
[+] Running 2/2
 ⠿ Network ingestion_server_default               Created                  0.0s
 ⠿ Container ingestion_server_ingestion_server_1  Started                  0.5s

Is the container name supposed to have ingestion_server repeated twice? Or is it because I ran it from ingestion_server directory?

[AetherUnbound]

@obulat you can also create the .env files with just env, although you shouldn't need to have them in order to run docker-compose pull 🤔 I'll look into that!

[obulat]

I also might have had a very old version of api locally...

[AetherUnbound]

Oh just kidding, it absolutely is expecting a .env file. This is for use in production so those values will need to be overridden anyway