Add Outline API client library foundation

Implements a first vertical slice of the Outline RPC API (auth, documents,
collections, users) covering the structural patterns used across the whole
API: single object, paginated list, tree, create/update, delete, search.
Chosen as the basis for future CLI and GUI clients built on top of this crate.

- Handwritten client (not codegen) against the vendored OpenAPI spec, since
  Outline's API is uniformly POST /api/<resource>.<action> with JSON bodies
  and inline/anonymous schemas that generators handle poorly
- Async (reqwest + tokio) Client, cheaply cloneable, no &mut self methods
- thiserror-based Error with ErrorKind classification and boxed API error
  context; forward-compatible models (unknown fields ignored, unknown
  string-enum values preserved via a catch-all variant) since the API is
  unversioned and self-hosted instances vary in age
- Pagination via Page<T>/Paginator with next_page/collect_all/into_stream
- wiremock-based test suite plus a spec-coverage test guarding against typos
  in RPC method names

src/models/team.rs

@@ -0,0 +1,78 @@
+use serde::{Deserialize, Serialize};
+
+use super::common::Id;
+use super::user::{User, UserRole};
+
+/// The payload returned by `auth.info`: the current API actor and their workspace.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[non_exhaustive]
+pub struct AuthInfo {
+    /// The user associated with the current API key or access token.
+    pub user: User,
+    /// The workspace the user belongs to.
+    pub team: Team,
+}
+
+/// An Outline workspace (formerly "team").
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+#[non_exhaustive]
+pub struct Team {
+    /// Unique identifier for the workspace.
+    pub id: Id,
+    /// The name of the workspace.
+    pub name: String,
+    /// A short description of the workspace.
+    #[serde(default)]
+    pub description: Option<String>,
+    /// The URL of the workspace's avatar image, if any.
+    #[serde(default)]
+    pub avatar_url: Option<String>,
+    /// Whether this workspace has share links globally enabled.
+    #[serde(default)]
+    pub sharing: bool,
+    /// The default role assigned to new members.
+    #[serde(default)]
+    pub default_user_role: Option<UserRole>,
+    /// The fully qualified URL at which this workspace can be accessed.
+    #[serde(default)]
+    pub url: Option<String>,
+    /// The subdomain at which this workspace can be accessed.
+    #[serde(default)]
+    pub subdomain: Option<String>,
+}
+
+/// Authentication configuration for an Outline instance (`auth.config`).
+///
+/// This endpoint requires no authentication and is useful for discovering
+/// available sign-in methods before a client has credentials.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+#[non_exhaustive]
+pub struct AuthConfig {
+    /// The name of the workspace.
+    #[serde(default)]
+    pub name: Option<String>,
+    /// The hostname at which this workspace can be accessed.
+    #[serde(default)]
+    pub hostname: Option<String>,
+    /// Available single sign-on services.
+    #[serde(default)]
+    pub services: Vec<AuthService>,
+}
+
+/// A single sign-on service available for authentication.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+#[non_exhaustive]
+pub struct AuthService {
+    /// The service identifier, e.g. `"slack"`.
+    #[serde(default)]
+    pub id: Option<String>,
+    /// The human-readable service name, e.g. `"Slack"`.
+    #[serde(default)]
+    pub name: Option<String>,
+    /// The URL to redirect to in order to authenticate with this service.
+    #[serde(default)]
+    pub auth_url: Option<String>,
+}