v0.15.0 (#3627)

Also updates the README to:
 - highlight Dendrite is in maintenance mode
- remove references to being "scalable" as we eventually decided to
focus on smaller deployments not huge ones.
- remove the progress section as it was horribly outdated and in general
Dendrite is roughly feature complete with synapse (with the exception of
sliding sync and OIDC, which is also now mentioned explicitly)

README.md

@@ -2,14 +2,14 @@
 
 [![Build status](https://github.com/element-hq/dendrite/actions/workflows/dendrite.yml/badge.svg?event=push)](https://github.com/element-hq/dendrite/actions/workflows/dendrite.yml) [![Dendrite](https://img.shields.io/matrix/dendrite:matrix.org.svg?label=%23dendrite%3Amatrix.org&logo=matrix&server_fqdn=matrix.org)](https://matrix.to/#/#dendrite:matrix.org) [![Dendrite Dev](https://img.shields.io/matrix/dendrite-dev:matrix.org.svg?label=%23dendrite-dev%3Amatrix.org&logo=matrix&server_fqdn=matrix.org)](https://matrix.to/#/#dendrite-dev:matrix.org)
 
-Dendrite is a second-generation Matrix homeserver written in Go.
-It intends to provide an **efficient**, **reliable** and **scalable** alternative to [Synapse](https://github.com/matrix-org/synapse):
+Dendrite is a second-generation Matrix homeserver written in Go. It is currently in maintenance mode,
+meaning only security fixes are being applied, for example [room version 12](https://matrix.org/blog/2025/08/security-release/).
+
+It intends to provide an **efficient** and **reliable** alternative to [Synapse](https://github.com/matrix-org/synapse):
 
 - Efficient: A small memory footprint with better baseline performance than an out-of-the-box Synapse.
 - Reliable: Implements the Matrix specification as written, using the
-  [same test suite](https://github.com/matrix-org/sytest) as Synapse as well as
-  a [brand new Go test suite](https://github.com/matrix-org/complement).
-- Scalable: can run on multiple machines and eventually scale to massive homeserver deployments.
+  [same](https://github.com/matrix-org/sytest) test [suites](https://github.com/matrix-org/complement) as Synapse.
 
 Dendrite is **beta** software, which means:
 
@@ -31,6 +31,10 @@ If you have further questions, please take a look at [our FAQ](docs/FAQ.md) or j
 - **[#dendrite-dev:matrix.org](https://matrix.to/#/#dendrite-dev:matrix.org)** - The place for developers, where all Dendrite development discussion happens
 - **[#dendrite-alerts:matrix.org](https://matrix.to/#/#dendrite-alerts:matrix.org)** - Release notifications and important info, highly recommended for all Dendrite server admins
 
+Dendrite does not currently support the following MSCs, which impacts the ability to use Element X with Dendrite servers:
+ - [MSC4186](https://github.com/matrix-org/matrix-spec-proposals/pull/4186): Simplified Sliding Sync
+ - [MSC3861](https://github.com/matrix-org/matrix-spec-proposals/pull/3861): Next-gen auth OIDC
+
 ## Requirements
 
 See the [Planning your Installation](https://element-hq.github.io/dendrite/installation/planning) page for
@@ -83,36 +87,6 @@ $ ./bin/create-account --config dendrite.yaml --username alice
 
 Then point your favourite Matrix client at `http://localhost:8008` or `https://localhost:8448`.
 
-## Progress
-
-We use a script called "Are We Synapse Yet" which checks Sytest compliance rates. Sytest is a black-box homeserver
-test rig with around 900 tests. The script works out how many of these tests are passing on Dendrite and it
-updates with CI. As of January 2023, we have 100% server-server parity with Synapse, and the client-server parity is at 93% , though check
-CI for the latest numbers. In practice, this means you can communicate locally and via federation with Synapse
-servers such as matrix.org reasonably well, although there are still some missing features (like SSO and Third-party ID APIs).
-
-We are prioritising features that will benefit single-user homeservers first (e.g Receipts, E2E) rather
-than features that massive deployments may be interested in (OpenID, Guests, Admin APIs, AS API).
-This means Dendrite supports amongst others:
-
-- Core room functionality (creating rooms, invites, auth rules)
-- Room versions 1 to 10 supported
-- Backfilling locally and via federation
-- Accounts, profiles and devices
-- Published room lists
-- Typing
-- Media APIs
-- Redaction
-- Tagging
-- Context
-- E2E keys and device lists
-- Receipts
-- Push
-- Guests
-- User Directory
-- Presence
-- Fulltext search
-
 ## Contributing
 
 We would be grateful for any help on issues marked as