Add logic around domain reputation flow

[odunayoogungbure-rgb]

resolves MSD-15158: Add logic around domain reputation flow

I used AI to generate parts of this PR

Yes

Changelist

• Add domain and account reputation events

Risks

None

Performance impact

None

Security impact

None

How to QA

1. Create a webhook with the reputation events (API only — no UI)

• Setup: mailersend/mailersend#8953 (and mailersend/mailersend#8847 under it) deployed to the environment you test against. Log in as an account admin, create an API token with Webhooks: Full access under API tokens, and copy a verified domain's ID from Domains. Open https://webhook.site and copy your URL.
• Steps: run this with your token, domain ID and URL:

MailerSend ms = new MailerSend();
ms.setToken("your_token");

Webhook webhook = ms.webhooks().builder()
    .name("Reputation webhook")
    .url("https://webhook.site/your-url")
    .enabled(true)
    .addEvent(WebhookEvents.DOMAIN_REPUTATION_CHANGED)
    .addEvent(WebhookEvents.ACCOUNT_REPUTATION_CHANGED)
    .createWebhook("domain_id");

Then in the app open Webhooks and click the new webhook.

• Expect: the call succeeds, and the webhook shows domain.reputation_changed and account.reputation_changed as its events.
• If broken: the builder throws a MailerSendException for an invalid event before calling the API.

Does not need QA:

• Other webhook events and endpoints (unchanged)

How to release

• Merge after mailersend/mailersend#8953 is deployed; the API rejects these events until then.
• Release a new minor version as usual.

Screenshots, recordings

N/A