Doc: Reset breaking changes and release notes for 9.0 (#16603)

docs/static/breaking-changes-70.asciidoc

@@ -1,5 +1,5 @@
 [[breaking-7.0]]
-=== Breaking changes in 7.0
+=== Breaking changes in 7.0 series
 
 Here are the breaking changes for {ls} 7.0. 
 

docs/static/breaking-changes-80.asciidoc

@@ -1,6 +1,20 @@
 [[breaking-8.0]]
+=== Breaking changes in 8.0 series 
+
+[discrete]
+[[breaking-8.15]]
+=== Breaking changes in 8.15
+
+*New {ls} SNMP integration plugin*
+
+Prior to 8.15.0, {ls} bundled stand-alone versions of the `input-snmp` and `input-snmptrap` plugins by default. 
+When you upgrade to 8.15.0, the stand-alone plugins are replaced by the 4.0.0+ version contained in the new SNMP integration plugin.
+
+IMPORTANT: Before you upgrade to {ls} 8.15.0, be aware of {logstash-ref}/plugins-integrations-snmp.html#plugins-integrations-snmp-migration[behavioral and mapping differences] between stand-alone plugins and the new versions included in the {logstash-ref}/plugins-integrations-snmp.html[SNMP integration plugin].
+If you need to maintain current mappings for the `input-snmptrap` plugin, you have some options to {logstash-ref}/plugins-integrations-snmp.html#plugins-integrations-snmp-input-snmptrap-compat[preserve existing behavior].
+
+[discrete]
 === Breaking changes in 8.0
-Here are the breaking changes for 8.0.
 
 [discrete]
 [[security-on-8.0]]

docs/static/breaking-changes-90.asciidoc

@@ -0,0 +1,15 @@
+[discrete] 
+[[breaking-9.0]]
+=== Breaking changes in 9.0
+coming[9.0.0]
+
+[discrete]
+[[sample-change-9.0]]
+===== Breaking change number one (sample) 
+
+Include:
+
+* change
+* user impact/decription/value prop
+* link to relevant docs for more information
+

docs/static/breaking-changes.asciidoc

@@ -1,30 +1,27 @@
 [[breaking-changes]]
 == Breaking changes
+coming[9.0.0]
 
 We strive to maintain backward compatibility between minor versions (8.x to 8.y,
 for example) so that you can upgrade without changing any configuration files.
-Breaking changes are usually introduced only between major versions (such as 7.x
+On occasion, we are forced to break compatibility within a given major release
-to 8.y). On occasion, we are forced to break compatibility within a given major release
 to ensure correctness of operation.
 
 This section covers the changes that you need to be aware of when migrating to
-Logstash 8.0.0 and later.
+Logstash 9.0.0 and later.
 
-NOTE: Migrating directly between non-consecutive major versions (6.x to
+NOTE: Migrating directly between non-consecutive major versions (7.x to
-8.x) is not recommended. 
+9.x) is not recommended. 
-We suggest that you upgrade to {prev-major-last} before you upgrade to 8.0.
+We suggest that you upgrade to the last release in the 8.x series before you upgrade to 9.0.
+// ToDo: Replace `last release in the 8.x series` in the previous statement with `{prev-major-last}`.
+// Hardcoding it for now to avoid confusion. 
 
-[discrete]
+Check out our <<releasenotes>> for additional release information.
-[[breaking-8.15]]
-=== 8.15
 
-*New {ls} SNMP integration plugin*
+// Include statement to pull in 9.0 breaking changes file
+// Add content for 9.0 breaking changes to `breaking-changes-90.asciidoc`, not here. 
 
-Prior to 8.15.0, {ls} bundled stand-alone versions of the `input-snmp` and `input-snmptrap` plugins by default. 
+include::breaking-changes-90.asciidoc[]
-When you upgrade to 8.15.0, the stand-alone plugins are replaced by the 4.0.0+ version contained in the new SNMP integration plugin.
-
-IMPORTANT: Before you upgrade to {ls} 8.15.0, be aware of {logstash-ref}/plugins-integrations-snmp.html#plugins-integrations-snmp-migration[behavioral and mapping differences] between stand-alone plugins and the new versions included in the {logstash-ref}/plugins-integrations-snmp.html[SNMP integration plugin].
-If you need to maintain current mappings for the `input-snmptrap` plugin, you have some options to {logstash-ref}/plugins-integrations-snmp.html#plugins-integrations-snmp-input-snmptrap-compat[preserve existing behavior].
 
 [discrete]
 === Breaking changes in earlier releases
@@ -41,4 +38,4 @@ include::breaking-changes-70.asciidoc[]
 include::breaking-changes-pre63.asciidoc[]
 include::breaking-changes-60.asciidoc[]
 
-Check out our <<releasenotes>> for additional release information.
+

docs/static/redirects.asciidoc

@@ -1,7 +1,7 @@
 ["appendix",role="exclude",id="redirects"]
 = Deleted pages
 
-The following pages have moved or been deleted.
+The pages in this section have been deleted or moved from another location.
 
 // MULTILINE FILTER