Add missing links (#1496)

## Description

<!-- ID for Jira ticket e.g [SPE-1234] -->

:ticket: N/A

<!-- Add a brief description of changes here. Include any other
necessary relevant links -->
- Fix reported missing links in WAF secure data doc
<!-- Help your reviewer understand the type of review you need by
selecting the scope and urgency. -->

### Requested review scope:

- [x] Content touched by the PR _only_ (typos, clarifications, tips)
- [ ] Code test (command and code block changes)
- [ ] Flow and language near changes (new/rearranged steps)
- [ ] Review everything (rewrites, major changes)

### Review urgency:

- [x] ASAP (bug fixes, broken content, imminent releases)
- [ ] 3 days (small changes, easy reviews)
- [ ] 1 week (default)
- [ ] Best effort (very non-urgent)

<!-- Fill out only the appropriate checklist for your type of feature
(or both if necessary) and delete the other one! -->

## All updates:

<!-- This section is mandatory for all PRs: -->

I have:

- [ ] Verified that all status checks have passed
- [ ] Verified that preview environment has successfully deployed
- [x] Verified appropriate `label` applied (`hcp` + `product name`)
- [x] Added all required reviewers (code owners and external)


[SPE-1234]:
https://hashicorp.atlassian.net/browse/SPE-1234?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: cjobermaier

content/well-architected-framework/docs/docs/secure-systems/data/protect-data-at-rest.mdx

@@ -27,18 +27,17 @@ For example, you can use Vault to issue your CI/CD pipeline dynamic credentials
 
 HashiCorp resources:
 
-- Learn to use Vault dynamic secrets
-- Learn to use versioned key/value secrets engine
-- Read how to retrieve CI/CD secrets from Vault.
-- Read the Vault's Key/Value (KV) secrets engine documentation
-- Enable transparent data encryption for Microsoft SQL with Vault
+- [Learn to use Vault dynamic secrets](/vault/tutorials/db-credentials)
+- [Learn to use versioned key/value secrets engine](/vault/tutorials/secrets-management/versioned-kv)
+- [Securely store secrets for CI/CD pipelines](/well-architected-framework/secure-systems/secure-applications/ci-cd-secrets)
+- [Vault Key/Value (KV) secrets engine documentation](/vault/docs/secrets/kv/kv-v2)
+- [Enable transparent data encryption for Microsoft SQL with Vault](/vault/docs/platform/mssql)
 
 External resources:
 
 - [Bank of New York Mellon Investigated for Lost Data Tape](https://www.bankinfosecurity.com/bank-new-york-mellon-investigated-for-lost-data-tape-a-862)
 - [What are cloud leaks?](https://www.upguard.com/blog/what-are-cloud-leaks)
-- Advanced Encryption Standard and Galois Counter Mode
-- Why you should use ephemeral credentials
+- [NIST Block Cipher Techniques](https://csrc.nist.gov/projects/block-cipher-techniques/bcm/current-modes)
 
 ## Next steps