Scale vertically email fetcher

[zieddhf]

• We have to approaches to manage resources triggered by S3 upload triggers

1. Using DigitalOcean API DOTS
2. Using Github Actions and Terraform

• We decided to implement the first approach since its faster to manage resource than the 2nd one.
  Terraform + Github actions loses a good amount of time to preapre the environment where the execution will take in place, and between different Terraform actions (init, plan, apply, state...)

• For 1st approach we can use either Dots the official Do API, or it's wrapper made by DO community

[zieddhf]

Usefull docs:

• https://www.digitalocean.com/blog/dots-sdk-development-automating-typescript-client-generation

• https://docs.digitalocean.com/products/app-platform/reference/app-spec/

• https://docs.digitalocean.com/products/app-platform/reference/

DO API (2.0):

• https://docs.digitalocean.com/reference/api/digitalocean/

[baderdean]

Other options:

• more RAM
• more Swap
• converting PST to mbox (readpst) then parsing mbox files
• using another library

[baderdean]

Proposed acceptance criteria

• Email fetcher scales vertically via configurable concurrency/resources without code changes.
• Throughput improves measurably under controlled load compared to current baseline.
• No regression in task correctness (no duplicate processing or dropped messages).
• Resource limits/knobs are documented for self-hosted and managed deployments.
• Basic stress/regression test evidence is attached to the issue or PR.