Docs: Replace blockdiag/seqdiag with Mermaid

Replace the abandoned sphinxcontrib-blockdiag and sphinxcontrib-seqdiag
Sphinx extensions with sphinxcontrib-mermaid in docs configuration.

None of the documentation in this repository uses blockdiag or seqdiag
directives; this is a config-only cleanup.

Issue-ID: CIMAN-33
Change-Id: I19a86a240d4dd7b530013b34b50508f2bd12a9b8
Signed-off-by: Claude <noreply@anthropic.com>
Signed-off-by: Matthew Watkins <mwatkins@linuxfoundation.org>

Author: ModeSevenIndustrialSolutions

docs/conf.py

@@ -19,8 +19,7 @@
 extensions = [
     'sphinx.ext.intersphinx',
     'sphinx.ext.graphviz',
-    'sphinxcontrib.blockdiag',
-    'sphinxcontrib.seqdiag',
+    'sphinxcontrib.mermaid',
     'sphinxcontrib.plantuml'
 ]
 

docs/requirements-docs.txt

@@ -1,7 +1,6 @@
 sphinx>=4.2.0  # BSD
 sphinx-rtd-theme>=1.0.0  # MIT
-sphinxcontrib-blockdiag  # BSD
-sphinxcontrib-seqdiag # BSD
+sphinxcontrib-mermaid>=1.0.0
 sphinxcontrib-spelling
 sphinxcontrib-plantuml
 six

docs/tox.ini

@@ -4,28 +4,25 @@ envlist = docs,docs-linkcheck,docs-spellcheck
 skipsdist = true
 
 [testenv:docs]
-basepython = python3.8
+basepython = python3.13
 deps =
     -r{toxinidir}/requirements-docs.txt
-    -chttps://releases.openstack.org/constraints/upper/yoga
     -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt?h=master
 commands =
     sphinx-build -W -q -b html -n -d {envtmpdir}/doctrees {toxinidir} {toxinidir}/_build/html
 
 [testenv:docs-linkcheck]
-basepython = python3.8
+basepython = python3.13
 deps =
     -r{toxinidir}/requirements-docs.txt
-    -chttps://releases.openstack.org/constraints/upper/yoga
     -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt?h=master
 commands =
     sphinx-build -W -q -b linkcheck -d {envtmpdir}/doctrees {toxinidir} {toxinidir}/_build/linkcheck
 
 [testenv:docs-spellcheck]
-basepython = python3.8
+basepython = python3.13
 deps =
     -r{toxinidir}/requirements-docs.txt
-    -chttps://releases.openstack.org/constraints/upper/yoga
     -chttps://git.onap.org/doc/plain/etc/upper-constraints.onap.txt?h=master
 commands =
     sphinx-build -W -q -b spelling -d {envtmpdir}/doctrees {toxinidir} {toxinidir}/_build/spellcheck