Setup mailman3 server

We want to migrate to mailman3 as mailman2 is basically unmaintained and requires Python 2 which is EOL.

Because the mailman and mailman3 packages conflict and we don't want to perform a big bang migration, mailman3 must be deployed on a separate server. mailman-web (mailman3's web interface) hasn't been packaged yet, so for now we are using my homebrewed PKGBUILD.

[1] https://gist.github.com/klausenbusk/5982063f95c503754a51ed2fefb8915e

Ref #59 (closed)

---

Migrated lists:

• arch-announce
• arch-devops-private
• arch-events
• arch-wiki-admins

group_vars/all/vault_mailman3.yml

 $ANSIBLE_VAULT;1.1;AES256
-34386532346634376634376461353464396132666530366431613130613931366634643438633735
-3462663739613064623538306432623132373833613538330a626166323436663430633861323036
-65626161336564643539313335363962646164633161393532376263336135323631653232616235
-3066353432336636340a626631643830313261656163373137626332633036376435396433616133
-37363462653066333133386439396637396233653232653736383061663531336536633863363635
-62373338326638363132393730643231376639313863366334613931633239323362303730303737
-35303562626635336165643736633061383235636333353762373061323664383763363736353939
-62346533666635326439326365383433383433633562663964316431346366393065323635393465
-35636330303630376566336635633361356336336331383863316532316234363861613338343534
-33653264363930373030383166653966633237356461633561393635383433663236643362303062
-64356233363034623137613964343735303538353430393363373736323136653561643762666134
-36323633356437333238353064303863353262666564633531353066323762306662363130323032
-65396632373631343332313238313837373032386639343135343262376237663261626435653236
-34313030646138393838366163633234656339303162613331626265663035303439306538626533
-31303331356538373365333436306337333936376361346439336363646230303331396637666334
-30343330373730373631336630653064343439336666636535666638393765306231366530613236
-33643862303537333930653932396139623139313938336166613266386661313365336639363731
-39303533316431363539386633313937386566353431363733633833333563663636396431653634
-33643030616136303165643861363434303333366365346361663333626661363061396437393062
-63653431316262626464626665643733656335316235613661663134616161393765646639386662
-63643430376432643730613236646636613261373139323362633461343765353139366638313061
-3736616530353539366437343865613934303431633739333162
+34383835323639306337626539636433613539636466653630383234333063623930666137646438
+6631373661313934656531363265363061313132633031650a326434306636396139663436623133
+38303738636465343430396461353533336165353033356430613036623136353137316338363364
+6563386438653733610a636566326462346364323362666639373430626663353935393763343638
+34393436616131376639653238326266336161393130386232373836303831646133303133313639
+65666136303433636632663261363930626161623938353033623761663264643831353063616432
+61373963636164663832666532313833656133363434323831323364643561616134616536646538
+30363632366661333936663139666166303737316166383738653038343034396265313466643532
+64646532393239613631653336633361346664343561643734316336363632383935653534323263
+38616463366235366636633839663464393562316138343534666430643266663439363838353239
+65643030666564343661343466646333313566333561646662623731656666353166626566333637
+31656432613439366661343834636239356139663263303965653430336662396431643966303739
+37316166663132363062323533646131623630666332653565303630613039666231323130386139
+34393639366537343463393133643832653133333065363839663333366333626132306636663136
+36316464623664303762316461386235643363353262323535383065346563613261623966313530
+37303466623834333537346265323766633934366332396436643962306637643262343463383963
+39393332633465333864346437383533633465343632323061623833393739646361383766656131
+31393066633364646637333765303266363438373330326334323666653262396137363036373734
+38663339326435383730366532363264386334376533653030343430633836376261346237646638
+37663864633832623237623335313938616562356366303638386531323035613534323130333439
+31613931636238373864303166623636643735383837343464323663633263313963626632633031
+64626535333231623461656661323264636333613430366637333631306663343438353763393537
+37663034336338376538333632623939643165613836656334323638653133333362393632653131
+38663937633065313531376134333238346163636162386665306332363635653934363761396339
+3366