Added notes about Hashicorp Vault to the KB

knowledge base/vault.md

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+# Hashicorp Vault
+
+## TL;DR
+
+```shell
+# Install the CLI.
+brew tap hashicorp/tap && brew install hashicorp/tap/vault
+
+# Settings.
+export VAULT_ADDR='https://vault.address/'
+export VAULT_NAMESPACE='namespace_name'
+
+# Check the connection to the Vault server.
+vault status
+
+# Login.
+vault login
+vault login -method='oidc'
+
+# Unwrap a token.
+# This operation may only be attempted once; after this attempt, the token will
+# die and will need to be regenerated.
+export VAULT_TOKEN='s.WVDAitOTTTfcjlklwk8AADDs' && vault unwrap
+
+# Create a secret.
+vault kv put secret/demo-app/config username='foo' password='bar'
+
+# Get a secret.
+# Note: "data" need to be added here in the path (secret/demo-app/config), as
+# it is a property of the Vault API.
+vault read -format 'json' 'secret/data/demo-app/config'
+```
+
+## Further readings
+
+- [HashiCorp Vault]
+
+<!-- -->
+[hashicorp vault]: https://www.vaultproject.io/