Attach yamlls to yaml.ansible filetypes & show diagnostic source

similiar to lsp source

templates/nvim/lua/lsp.lua.j2

@@ -29,7 +29,6 @@ end
 
 --enable some language servers with the additional completion capabilities
 --offered by nvim-cmp
--- TODO: use `.join`?
 local servers = {
   {% for item in language_servers %}
   {% if item.auto_setup and not loop.last %}
@@ -61,33 +60,39 @@ local python_root_dir = function(fname)
     util.path.dirname(fname)
 end
 
-nvim_lsp.ruff.setup({
+nvim_lsp.ruff.setup {
   on_attach = on_attach,
   capabilities = capabilities,
   root_dir = python_root_dir
-})
+}
 
 
-nvim_lsp.pyright.setup({
+nvim_lsp.pyright.setup {
   settings = {
     pyright = {
       -- Using Ruff's import organizer
       disableOrganizeImports = true,
     },
   },
-})
+}
 
-nvim_lsp.html.setup({
+nvim_lsp.html.setup {
   on_attach = on_attach,
   capabilities = capabilities,
   filetypes = { 'html', 'htmldjango' },
-})
+}
 
 {% endif %}
+nvim_lsp.yamlls.setup {
+  on_attach = on_attach,
+  capabilities = capabilities,
+  filetypes = { 'yaml', 'yaml.ansible', 'yaml.docker-compose', 'yaml.gitlab' }
+}
+
 local cmp = require('cmp')
 local luasnip = require('luasnip')
 
-cmp.setup({
+cmp.setup {
   sources = {
     { name = 'nvim_lsp', },
     { name = 'buffer' },
@@ -148,14 +153,15 @@ cmp.setup({
       luasnip.lsp_expand(args.body)
     end,
   },
-})
+}
 
-vim.diagnostic.config({
+vim.diagnostic.config {
   float = {
-    source = 'always',
-    border = border
+    suffix = function(diagnostic)
+      return (' %s | [%s]'):format(diagnostic.code, diagnostic.source)
+    end
   },
-})
+}
 
 local enable_formatting = os.getenv("ENABLE_FORMATTING", False)