web: Replace calls to rootInterface()?.tenant? with a contextual this.tenant object (#7778)

* This commit abstracts access to the object `rootInterface()?.config?` into a single accessor,
`authentikConfig`, that can be mixed into any AKElement object that requires access to it.

Since access to `rootInterface()?.config?` is _universally_ used for a single (and repetitive)
boolean check, a separate accessor has been provided that converts all calls of the form:

``` javascript
rootInterface()?.config?.capabilities.includes(CapabilitiesEnum.CanImpersonate)
```

into:

``` javascript
this.can(CapabilitiesEnum.CanImpersonate)
```

It does this via a Mixin, `WithCapabilitiesConfig`, which understands that these calls only make
sense in the context of a running, fully configured authentik instance, and that their purpose is to
inform authentik components of a user’s capabilities. The latter is why I don’t feel uncomfortable
turning a function call into a method; we should make it explicit that this is a relationship
between components.

The mixin has a single single field, `[WCC.capabilitiesConfig]`, where its association with the
upper-level configuration is made. If that syntax looks peculiar to you, good! I’ve used an explict
unique symbol as the field name; it is inaccessable an innumerable in the object list. The debugger
shows it only as:

    Symbol(): {
        cacheTimeout: 300
        cacheTimeoutFlows: 300
        cacheTimeoutPolicies: 300
        cacheTimeoutReputation: 300
        capabilities: (5) ['can_save_media', 'can_geo_ip', 'can_impersonate', 'can_debug', 'is_enterprise']
    }

Since you can’t reference it by identity, you can’t write to it. Until every browser supports actual
private fields, this is the best we can do; it does guarantee that field name collisions are
impossible, which is a win.

The mixin takes a second optional boolean; setting this to true will cause any web component using
the mixin to automatically schedule a re-render if the capabilities list changes.

The mixin is also generic; despite the "...into a Lit-Context" in the title, the internals of the
Mixin can be replaced with anything so long as the signature of `.can()` is preserved.

Because this work builds off the work I did to give the Sidebar access to the configuration without
ad-hoc retrieval or prop-drilling, it wasn’t necessary to create a new context for it. That will be
necessary for the following:

TODO:

``` javascript
rootInterface()?.uiConfig;
rootInterface()?.tenant;
me();
```

* This commit abstracts access to the object `rootInterface()?.tenant?` into a single accessor,
`tenant`, that can be mixed into any AKElement object that requires access to it.

Like `WithCapabilitiesConfig` and `WithAuthentikConfig`, this one is named `WithTenantConfig`.

TODO:

``` javascript
rootInterface()?.uiConfig;
me();
```

* web: Added a README with a description of the applications' "mental model," essentially an architectural description.

* web: prettier did a thing

* web: prettier had opinions about the README

* web: Jens requested that subscription be  by default, and it's the right call.

* web: Jens requested that the default subscription state for contexts be , and it's the right call.

* web: prettier having opinions after merging with dependent branch

* web: prettier still having opinions.

web/src/admin/applications/wizard/methods/ldap/ak-application-wizard-authentication-by-ldap.ts

@@ -7,7 +7,7 @@ import "@goauthentik/components/ak-number-input";
 import "@goauthentik/components/ak-radio-input";
 import "@goauthentik/components/ak-switch-input";
 import "@goauthentik/components/ak-text-input";
-import { rootInterface } from "@goauthentik/elements/Base";
+import { WithTenantConfig } from "@goauthentik/elements/Interface/tenantProvider";
 import "@goauthentik/elements/forms/FormGroup";
 import "@goauthentik/elements/forms/HorizontalFormElement";
 
@@ -32,7 +32,7 @@ import {
 } from "./LDAPOptionsAndHelp";
 
 @customElement("ak-application-wizard-authentication-by-ldap")
-export class ApplicationWizardApplicationDetails extends BaseProviderPanel {
+export class ApplicationWizardApplicationDetails extends WithTenantConfig(BaseProviderPanel) {
     render() {
         const provider = this.wizard.provider as LDAPProvider | undefined;
         const errors = this.wizard.errors.provider;
@@ -57,7 +57,7 @@ export class ApplicationWizardApplicationDetails extends BaseProviderPanel {
                     <ak-tenanted-flow-search
                         flowType=${FlowsInstancesListDesignationEnum.Authentication}
                         .currentFlow=${provider?.authorizationFlow}
-                        .tenantFlow=${rootInterface()?.tenant?.flowAuthentication}
+                        .tenantFlow=${this.tenant.flowAuthentication}
                         required
                     ></ak-tenanted-flow-search>
                     <p class="pf-c-form__helper-text">