Expand and document PSRT coordination process (#1769)

* Expand and document PSRT coordination process

* Apply suggestions from code review

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

* Add 'mermaid' diagram sources, clarify patch development responsibility

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix graphic in dark mode

* Apply suggestions from code review

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

* Use ASCII art instead of Mermaid

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 4 people

_static/psrt-coordinator-report.html

@@ -0,0 +1,31 @@
+<!-- Centering a div -->
+<div style="width: 100%; text-align: center;">
+<div style="display: inline-block; text-align: left;">
+<code><pre>
+          ┌────────────────────────┐
+          │  Received a report...  │
+          └──┬──────────────────┬──┘
+             │                  │
+┌────────────▼──────────────┐ ┌─▼──────────┐
+│ ..via security@python.org │ │ ..via GHSA │
+└────────────┬──────────────┘ └─┬──────────┘
+             │                  │
+┌────────────▼──────────────┐   │
+│  PSRT admin reviews email │   │
+└───┬───────────────────┬───┘   │
+    │                   │       │
+┌───▼────┐         ┌────▼───┐   │
+│ Reject │         │ Accept │   │
+└────────┘         └────┬───┘   │
+                        │       │
+┌───────────────────────▼───┐   │
+│   PSRT asks reporter to   │   │
+│       open via GHSA       │   │
+└────────────┬──────────────┘   │
+             │                  │
+          ┌──▼──────────────────▼──┐
+          │ GHSA in state 'Triage' │
+          └────────────────────────┘
+</pre></code>
+</div>
+</div>

_static/psrt-coordinator-triage.html

@@ -0,0 +1,40 @@
+<!-- Centering a div -->
+<div style="width: 100%; text-align: center;">
+<div style="display: inline-block; text-align: left;">
+<code><pre>
+                 ┌────────────────────────┐
+                 │ GHSA in state 'Triage' │
+                 └─┬────────────────────┬─┘
+                   │                    │
+┌──────────────────▼─────────┐ ┌────────▼───────────────────┐
+│                            │ │   After 3 days idle,       │
+│    PSRT member volunteers  │ │   Coordinator is assigned  │
+│    as Coordinator          │ │   automatically by bot     │
+└──────────────────┬─────────┘ └────────┬───────────────────┘
+                   │                    │
+                 ┌─▼────────────────────▼─┐
+                 │  GHSA update 'Credit'  │
+                 │  field to Coordinator  │
+                 └────────────┬───────────┘
+                              │
+                 ┌────────────▼───────────┐
+                 │ Coordinator determines │
+             ┌───┤    whether report...   ┼───┐
+             │   └────────────┬───────────┘   │
+             │                │               │
+┌────────────▼─┐ ┌────────────▼───────────┐ ┌─▼─────────────┐
+│..is a invalid│ │  ..is a bug, but not   │ │..is a security│
+│  or non-issue│ │    security relevant   │ │     issue     │
+└────────────┬─┘ └────────────┬───────────┘ └─┬─────────────┘
+             │                │               │
+             │   ┌────────────▼───────────┐   │
+             │   │   Coordinator opens a  │   │
+             │   │   public GitHub issue  │   │
+             │   └─┬──────────────────────┘   │
+             │     │                          │
+  ┌──────────▼─────▼───────┐     ┌────────────▼───────────┐
+  │ Close the GHSA ticket  │     │  GHSA in state 'Draft' │
+  └────────────────────────┘     └────────────────────────┘
+</pre></code>
+</div>
+</div>