UI: Add PKI readme and changelog for UI improvements (#20706)

* update pki readme

* add readme

* make it fancier

* add more info

* add config improvements to entry

* move changelog info to release notes

* reword action summary

* stop yelling in bullet points

* update action

changelog/pki-ui-improvements.txt

@@ -0,0 +1,3 @@
+```release-note:feature
+**NEW PKI Workflow in UI**: Completes generally available rollout of new PKI UI that provides smoother mount configuration and a more guided user experience
+```

ui/app/models/pki/certificate/base.js

@@ -14,8 +14,8 @@ import lazyCapabilities, { apiPath } from 'vault/macros/lazy-capabilities';
  * The base certificate model contains shared attributes that make up a certificate's content.
  * Other models under pki/certificate will extend this model and include additional attributes
  * and associated adapter methods for performing various generation and signing actions.
- * This model also displays leaf certs and their parsed attributes (parsed parameters only
- * render if included in certDisplayFields below).
+ * This model also displays leaf certs and their parsed attributes (which exist as an object in
+ * the attribute `parsedCertificate`)
  */
 
 // also displays parsedCertificate values in the template

ui/lib/pki/README.md

@@ -10,24 +10,48 @@ The [Vault PKI Secrets Engine](https://developer.hashicorp.com/vault/api-docs/se
 
 ## About the UI engine
 
-If you couldn't tell from the documentation above, PKI is _complex_. As such, the data doesn't map cleanly to a CRUD model and so the first thing you might notice is that the models and adapters for PKI (which [live in the main app](https://ember-engines.com/docs/addons#using-ember-data), not the engine) have some custom logic that differentiate it from most other secret engines. Below are the model
+If you couldn't tell from the documentation above, PKI is _complex_. As such, the data doesn't map cleanly to a CRUD model and so the first thing you might notice is that the models and adapters for PKI (which [live in the main app](https://ember-engines.com/docs/addons#using-ember-data), not the engine) have some custom logic that differentiate it from most other secret engines. Below are the models used throughout PKI and how they are used to interact with the mount. Aside from `pki/action`, each model has a corresponding tab in the UI that takes you to its `LIST` view.
 
-### pki/key
+- ### [pki/action](../../app/models/pki/action.js)
 
-TBD
+  This model is used to perform different `POST` requests that receive similar parameters but don't create a single item (which would be a record in Ember data). These various actions may create multiple items that contain different attributes than those submitted in the `POST` request. For example:
 
-### pki/role
+  > - `POST pki/generate/root/:type` creates a new self-signed CA certificate (an issuer) and private key, which is only returned if `type = exported`
+  > - `POST pki/issuer/:issuer_ref/sign-intermediate` creates a certificate, and returns issuing CA and CA chain data that is only available once
 
-TBD
+  The `pki/action`[adapter](../../app/adapters/pki/action.js) is used to map the desired action to the corresponding endpoint, and the `pki/action` [serializer](../../app/serializers/pki/action.js) includes logic to send the relevant attributes. The following PKI workflows use this model:
 
-### pki/issuer
+  - [Root generation and rotation](https://developer.hashicorp.com/vault/api-docs/secret/pki#generate-root)
+  - [Import CA cert and keys](https://developer.hashicorp.com/vault/api-docs/secret/pki#import-ca-certificates-and-keys)
+  - [Generate intermediate CSR](https://developer.hashicorp.com/vault/api-docs/secret/pki#generate-intermediate-csr)
+  - [Sign intermediate](https://developer.hashicorp.com/vault/api-docs/secret/pki#sign-intermediate)
 
-TBD
+- ### [pki/certificate/base](../../app/models/pki/certificate/base.js)
 
-### pki/certificate/\*
+  This model is for specific interactions with certificate data. The base model contains attributes that make up a certificate's content. The other models that extend this model [certificate/generate](../../app/models/pki/certificate/generate.js) and [certificate/sign](../../app/models/pki/certificate/sign.js) include additional attributes to perform their relevant requests.
 
-TBD
+  The `parsedCertificate` attribute is an object that houses all of the parsed certificate data returned by the [parse-pki-cert.js](../../app/utils/parse-pki-cert.js) util.
 
-### pki/action
+> _The following models more closely follow a CRUD pattern:_
 
-TBD
+- ### [pki/issuer](../../app/models/pki/issuer.js)
+
+  > _Issuers are created by the `pki/action` model by either [importing a CA](https://developer.hashicorp.com/vault/api-docs/secret/pki#import-ca-certificates-and-keys) or [generating a root](https://developer.hashicorp.com/vault/api-docs/secret/pki#generate-root)_
+
+  - [update](https://developer.hashicorp.com/vault/api-docs/secret/pki#read-issuer-certificate)
+  - [read](https://developer.hashicorp.com/vault/api-docs/secret/pki#read-issuer-certificate)
+  - [list](https://developer.hashicorp.com/vault/api-docs/secret/pki#list-issuers)
+
+- ### [pki/role](../../app/models/pki/role.js)
+
+  - [create/update](https://developer.hashicorp.com/vault/api-docs/secret/pki#create-update-role)
+  - [read](https://developer.hashicorp.com/vault/api-docs/secret/pki#read-role)
+  - [list](https://developer.hashicorp.com/vault/api-docs/secret/pki#list-roles)
+
+- ### [pki/key](../../app/models/pki/key.js)
+
+  - `CREATE` has two options:
+    - [generate](https://developer.hashicorp.com/vault/api-docs/secret/pki#import-ca-certificates-and-keys)
+    - [import](https://developer.hashicorp.com/vault/api-docs/secret/pki#import-key)
+  - [read](https://developer.hashicorp.com/vault/api-docs/secret/pki#read-key)
+  - [list](https://developer.hashicorp.com/vault/api-docs/secret/pki#list-keys)